nb/intel/sandybridge: Add x86_64 support

Fix compilation on x86_64 by using compatible types.
The MRC blob isn't supported yet as there's no x86_32 wrapper.

Tested on HP8200:
* Still boots on x86_32.
* Boots to payload in x86_64

Change-Id: Iab29a87d52ad3f6c480f21a3b8389a7f49cb5dd8
Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/44677
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Paul Menzel <paulepanter@mailbox.org>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>

src/cpu/intel/model_206ax/Kconfig

@@ -3,9 +3,15 @@ config CPU_INTEL_MODEL_206AX
 
 if CPU_INTEL_MODEL_206AX
 
+config ARCH_EXP_X86_64
+	bool "Experimental 64bit support"
+	depends on USE_NATIVE_RAMINIT
+	default n
+
 config CPU_SPECIFIC_OPTIONS
 	def_bool y
-	select ARCH_ALL_STAGES_X86_32
+	select ARCH_ALL_STAGES_X86_32 if !ARCH_EXP_X86_64
+	select ARCH_ALL_STAGES_X86_64 if ARCH_EXP_X86_64
 	select BOOT_DEVICE_SPI_FLASH_NO_EARLY_WRITES
 	select MMX
 	select SSE2