console: Implement pre-console buffer

Allow redirection of console output prior to console initialisation to a
temporary buffer.

To enable this functionality, the board (or arch) must define:
 - CONFIG_PRE_CONSOLE_BUFFER - Enable pre-console buffer
 - CONFIG_PRE_CON_BUF_ADDR - Base address of pre-console buffer
 - CONFIG_PRE_CON_BUF_SZ - Size of pre-console buffer (in bytes)

The pre-console buffer will buffer the last CONFIG_PRE_CON_BUF_SZ bytes
Any earlier characters are silently dropped.
diff --git a/arch/arm/include/asm/global_data.h b/arch/arm/include/asm/global_data.h
index 4fc51fd..b85b7fe 100644
--- a/arch/arm/include/asm/global_data.h
+++ b/arch/arm/include/asm/global_data.h
@@ -38,6 +38,9 @@
 	unsigned long	flags;
 	unsigned long	baudrate;
 	unsigned long	have_console;	/* serial_init() was called */
+#ifdef CONFIG_PRE_CONSOLE_BUFFER
+	unsigned long	precon_buf_idx;	/* Pre-Console buffer index */
+#endif
 	unsigned long	env_addr;	/* Address  of Environment struct */
 	unsigned long	env_valid;	/* Checksum of Environment valid? */
 	unsigned long	fb_base;	/* base address of frame buffer */
diff --git a/arch/avr32/include/asm/global_data.h b/arch/avr32/include/asm/global_data.h
index 4ef8fc5..5c654bd 100644
--- a/arch/avr32/include/asm/global_data.h
+++ b/arch/avr32/include/asm/global_data.h
@@ -38,6 +38,9 @@
 	unsigned long	baudrate;
 	unsigned long	stack_end;	/* highest stack address */
 	unsigned long	have_console;	/* serial_init() was called */
+#ifdef CONFIG_PRE_CONSOLE_BUFFER
+	unsigned long	precon_buf_idx;	/* Pre-Console buffer index */
+#endif
 	unsigned long	reloc_off;	/* Relocation Offset */
 	unsigned long	env_addr;	/* Address of env struct */
 	unsigned long	env_valid;	/* Checksum of env valid? */
diff --git a/arch/blackfin/include/asm/global_data.h b/arch/blackfin/include/asm/global_data.h
index eba5e93..f7aa711 100644
--- a/arch/blackfin/include/asm/global_data.h
+++ b/arch/blackfin/include/asm/global_data.h
@@ -45,6 +45,9 @@
 	unsigned long board_type;
 	unsigned long baudrate;
 	unsigned long have_console;	/* serial_init() was called */
+#ifdef CONFIG_PRE_CONSOLE_BUFFER
+	unsigned long	precon_buf_idx;	/* Pre-Console buffer index */
+#endif
 	phys_size_t ram_size;		/* RAM size */
 	unsigned long env_addr;	/* Address  of Environment struct */
 	unsigned long env_valid;	/* Checksum of Environment valid? */
diff --git a/arch/m68k/include/asm/global_data.h b/arch/m68k/include/asm/global_data.h
index fc486fd..0ba2b43 100644
--- a/arch/m68k/include/asm/global_data.h
+++ b/arch/m68k/include/asm/global_data.h
@@ -57,6 +57,9 @@
 	unsigned long	env_addr;	/* Address  of Environment struct	*/
 	unsigned long	env_valid;	/* Checksum of Environment valid?	*/
 	unsigned long	have_console;	/* serial_init() was called		*/
+#ifdef CONFIG_PRE_CONSOLE_BUFFER
+	unsigned long	precon_buf_idx;	/* Pre-Console buffer index */
+#endif
 #if defined(CONFIG_LCD) || defined(CONFIG_VIDEO)
 	unsigned long	fb_base;	/* Base addr of framebuffer memory */
 #endif
diff --git a/arch/microblaze/include/asm/global_data.h b/arch/microblaze/include/asm/global_data.h
index 557ad27..6e8537c 100644
--- a/arch/microblaze/include/asm/global_data.h
+++ b/arch/microblaze/include/asm/global_data.h
@@ -39,6 +39,9 @@
 	unsigned long	flags;
 	unsigned long	baudrate;
 	unsigned long	have_console;	/* serial_init() was called */
+#ifdef CONFIG_PRE_CONSOLE_BUFFER
+	unsigned long	precon_buf_idx;	/* Pre-Console buffer index */
+#endif
 	unsigned long	env_addr;	/* Address  of Environment struct */
 	unsigned long	env_valid;	/* Checksum of Environment valid? */
 	unsigned long	fb_base;	/* base address of frame buffer */
diff --git a/arch/mips/include/asm/global_data.h b/arch/mips/include/asm/global_data.h
index 271a290..b193517 100644
--- a/arch/mips/include/asm/global_data.h
+++ b/arch/mips/include/asm/global_data.h
@@ -41,6 +41,9 @@
 	unsigned long	flags;
 	unsigned long	baudrate;
 	unsigned long	have_console;	/* serial_init() was called */
+#ifdef CONFIG_PRE_CONSOLE_BUFFER
+	unsigned long	precon_buf_idx;	/* Pre-Console buffer index */
+#endif
 	phys_size_t	ram_size;	/* RAM size */
 	unsigned long	reloc_off;	/* Relocation Offset */
 	unsigned long	env_addr;	/* Address  of Environment struct */
diff --git a/arch/nios2/include/asm/global_data.h b/arch/nios2/include/asm/global_data.h
index 2c4a719..d9f0664 100644
--- a/arch/nios2/include/asm/global_data.h
+++ b/arch/nios2/include/asm/global_data.h
@@ -29,6 +29,9 @@
 	unsigned long	baudrate;
 	unsigned long	cpu_clk;	/* CPU clock in Hz!		*/
 	unsigned long	have_console;	/* serial_init() was called */
+#ifdef CONFIG_PRE_CONSOLE_BUFFER
+	unsigned long	precon_buf_idx;	/* Pre-Console buffer index */
+#endif
 	phys_size_t	ram_size;	/* RAM size */
 	unsigned long	env_addr;	/* Address  of Environment struct */
 	unsigned long	env_valid;	/* Checksum of Environment valid */
diff --git a/arch/powerpc/include/asm/global_data.h b/arch/powerpc/include/asm/global_data.h
index a33ca2f..7fcaf38 100644
--- a/arch/powerpc/include/asm/global_data.h
+++ b/arch/powerpc/include/asm/global_data.h
@@ -138,6 +138,9 @@
 	unsigned long	env_addr;	/* Address  of Environment struct	*/
 	unsigned long	env_valid;	/* Checksum of Environment valid?	*/
 	unsigned long	have_console;	/* serial_init() was called		*/
+#ifdef CONFIG_PRE_CONSOLE_BUFFER
+	unsigned long	precon_buf_idx;	/* Pre-Console buffer index */
+#endif
 #if defined(CONFIG_SYS_ALLOC_DPRAM) || defined(CONFIG_CPM2)
 	unsigned int	dp_alloc_base;
 	unsigned int	dp_alloc_top;
diff --git a/arch/sh/include/asm/global_data.h b/arch/sh/include/asm/global_data.h
index 0c09ba9..1b782fc 100644
--- a/arch/sh/include/asm/global_data.h
+++ b/arch/sh/include/asm/global_data.h
@@ -34,6 +34,9 @@
 	unsigned long	baudrate;
 	unsigned long	cpu_clk;	/* CPU clock in Hz! */
 	unsigned long	have_console;	/* serial_init() was called */
+#ifdef CONFIG_PRE_CONSOLE_BUFFER
+	unsigned long	precon_buf_idx;	/* Pre-Console buffer index */
+#endif
 	phys_size_t	ram_size;	/* RAM size */
 	unsigned long	env_addr;	/* Address  of Environment struct */
 	unsigned long	env_valid;	/* Checksum of Environment valid */
diff --git a/arch/sparc/include/asm/global_data.h b/arch/sparc/include/asm/global_data.h
index 9b14674..a1e4b44 100644
--- a/arch/sparc/include/asm/global_data.h
+++ b/arch/sparc/include/asm/global_data.h
@@ -53,6 +53,9 @@
 	unsigned long env_valid;	/* Checksum of Environment valid?       */
 	unsigned long have_console;	/* serial_init() was called */
 
+#ifdef CONFIG_PRE_CONSOLE_BUFFER
+	unsigned long	precon_buf_idx;	/* Pre-Console buffer index */
+#endif
 #if defined(CONFIG_LCD) || defined(CONFIG_VIDEO)
 	unsigned long fb_base;	/* Base address of framebuffer memory   */
 #endif
diff --git a/arch/x86/include/asm/global_data.h b/arch/x86/include/asm/global_data.h
index f8a16d6..f177a4f 100644
--- a/arch/x86/include/asm/global_data.h
+++ b/arch/x86/include/asm/global_data.h
@@ -40,6 +40,9 @@
 	unsigned long	flags;
 	unsigned long	baudrate;
 	unsigned long	have_console;	/* serial_init() was called */
+#ifdef CONFIG_PRE_CONSOLE_BUFFER
+	unsigned long	precon_buf_idx;	/* Pre-Console buffer index */
+#endif
 	unsigned long	reloc_off;	/* Relocation Offset */
 	unsigned long	load_off;	/* Load Offset */
 	unsigned long	env_addr;	/* Address  of Environment struct */