arch/x86/include: rename smm.h to smm_call.h

Rename smm.h to smm_call.h to make including this file look less
ambiguous.

Signed-off-by: Felix Held <felix-coreboot@felixheld.de>
Change-Id: Ia907ad92459e835feeddf7eb4743a38f99549179
Reviewed-on: https://review.coreboot.org/c/coreboot/+/79833
Reviewed-by: Jérémy Compostella <jeremy.compostella@intel.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Matt DeVillier <matt.devillier@amd.corp-partner.google.com>
diff --git a/src/arch/x86/include/smm.h b/src/arch/x86/include/smm_call.h
similarity index 100%
rename from src/arch/x86/include/smm.h
rename to src/arch/x86/include/smm_call.h