Migrate CUSTOM_SYS_INIT_SP_ADDR to Kconfig using system-constants.h

- Make all users of CUSTOM_SYS_INIT_SP_ADDR reference SYS_INIT_SP_ADDR
- Introduce HAS_CUSTOM_SYS_INIT_SP_ADDR to allow for setting the stack
  pointer directly, otherwise we use the common calculation.
- On some platforms that were using the standard calculation but did not
  set CONFIG_SYS_INIT_RAM_SIZE / CONFIG_SYS_INIT_RAM_ADDR, set them.
- On a small number of platforms that were not subtracting
  GENERATED_GBL_DATA_SIZE do so now via the standard calculation.
- CONFIG_SYS_INIT_SP_OFFSET is now widely unused, so remove it from most
  board config header files.

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/include/configs/ethernut5.h b/include/configs/ethernut5.h
index 3231f3c..8e7bfad 100644
--- a/include/configs/ethernut5.h
+++ b/include/configs/ethernut5.h
@@ -22,10 +22,8 @@
 #define CONFIG_SYS_AT91_MAIN_CLOCK	18432000 /* 18.432 MHz crystal */
 
 /* 32kB internal SRAM */
-#define CONFIG_SRAM_BASE	0x00300000 /*AT91SAM9XE_SRAM_BASE */
-#define CONFIG_SRAM_SIZE	(32 << 10)
-#define CONFIG_SYS_INIT_SP_ADDR	(CONFIG_SRAM_BASE + CONFIG_SRAM_SIZE - \
-				GENERATED_GBL_DATA_SIZE)
+#define CONFIG_SYS_INIT_RAM_ADDR	0x00300000 /*AT91SAM9XE_SRAM_BASE */
+#define CONFIG_SYS_INIT_RAM_SIZE	(32 << 10)
 
 /* 128MB SDRAM in 1 bank */
 #define CONFIG_SYS_SDRAM_BASE		0x20000000