x86: select CONFIG_64BIT for X86_64

Select CONFIG_64BIT so that we pass the -m64 option (instead of -m32) to
static analysis tools.
Introduce CONFIG_SPL_64BIT and select it for architectures other than
x86 with 64 bit builds. Do not select it for x86 builds as x86 uses
a 32 bit SPL.
Ensure that when limits are set they use CONFIG_64BIT for U-Boot
proper and CONFIG_SPL_64BIT for SPL. This is to allow for the 32 bit
SPL build used by x86.

Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Signed-off-by: Andrew Goodbody <andrew.goodbody@linaro.org>
diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index 38577af..7ea439e 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -211,6 +211,7 @@
 	bool "MIPS64 Release 1"
 	depends on SUPPORTS_CPU_MIPS64_R1
 	select 64BIT
+	select SPL_64BIT if SPL
 	help
 	  Choose this option to build a kernel for release 1 through 5 of the
 	  MIPS64 architecture.
@@ -219,6 +220,7 @@
 	bool "MIPS64 Release 2"
 	depends on SUPPORTS_CPU_MIPS64_R2
 	select 64BIT
+	select SPL_64BIT if SPL
 	help
 	  Choose this option to build a kernel for release 2 through 5 of the
 	  MIPS64 architecture.
@@ -227,6 +229,7 @@
 	bool "MIPS64 Release 6"
 	depends on SUPPORTS_CPU_MIPS64_R6
 	select 64BIT
+	select SPL_64BIT if SPL
 	help
 	  Choose this option to build a kernel for release 6 or later of the
 	  MIPS64 architecture.
@@ -235,6 +238,7 @@
 	bool "Marvell Octeon series of CPUs"
 	depends on SUPPORTS_CPU_MIPS64_OCTEON
 	select 64BIT
+	select SPL_64BIT if SPL
 	help
 	 Choose this option for Marvell Octeon CPUs.  These CPUs are between
 	 MIPS64 R5 and R6 with other extensions.