Makefile.inc: Create a default SMMSTORE region

Change-Id: I7b7b75050e0139ea9a0a4f2ad3c0d69a482fb38b
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/c/30421
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>

util/cbfstool/default-x86.fmd

@@ -11,6 +11,7 @@ FLASH@##ROM_BASE## ##ROM_SIZE## {
 	BIOS@##BIOS_BASE## ##BIOS_SIZE## {
 		##CONSOLE_ENTRY##
 		##MRC_CACHE_ENTRY##
+		##SMMSTORE_ENTRY##
 		FMAP@##FMAP_BASE## ##FMAP_SIZE##
 		COREBOOT(CBFS)@##CBFS_BASE## ##CBFS_SIZE##
 	}