drivers/intel/fsp2_0/memory_init: Wrap calls into FSP

drivers/intel/fsp2_0/memory_init: Wrap calls into FSP

Use a wrapper code that does nothing on x86_32, but drops to protected
mode to call into FSP when running on x86_64.

Tested on Intel Skylake when running in long mode. Successfully run the
FSP-M which is compiled for x86_32 and then continued booting in
long mode.

Change-Id: I9fb37019fb0d04f74d00733ce2e365f484d97d66
Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/48202
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>