ironlake: Add support for x86_64

Allow to compile the experimental x86_64 code.

Tested on Lenovo Thinkpad T410.
Hangs in SMM relocation. When skipped boots into GNU/Linux.

Change-Id: I60f2fccba357cb5fb5d85feb4ee8d02abfe6bc7e
Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/45699
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-by: Christian Walter <christian.walter@9elements.com>

src/cpu/intel/model_2065x/Kconfig

@@ -5,6 +5,7 @@ if CPU_INTEL_MODEL_2065X
 
 config CPU_SPECIFIC_OPTIONS
 	def_bool y
+	select HAVE_EXP_X86_64_SUPPORT
 	select ARCH_X86
 	select BOOT_DEVICE_SPI_FLASH_NO_EARLY_WRITES
 	select SSE2