cpu/x86/smm: Promote smm_subregion()

No need to limit these declarations to FSP. Both
PARALLEL_MP_INIT smm_relocate() and TSEG_STAGE_CACHE
can be built on top of this.

Change-Id: I7b0b9b8c8bee03aabe251c50c47dc42f6596e169
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/34701
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
diff --git a/src/drivers/intel/fsp1_1/car.c b/src/drivers/intel/fsp1_1/car.c
index 19eb041..1b6f62c 100644
--- a/src/drivers/intel/fsp1_1/car.c
+++ b/src/drivers/intel/fsp1_1/car.c
@@ -19,9 +19,9 @@
 #include <commonlib/helpers.h>
 #include <cpu/intel/romstage.h>
 #include <cpu/x86/mtrr.h>
+#include <cpu/x86/smm.h>
 #include <fsp/car.h>
 #include <fsp/util.h>
-#include <fsp/memmap.h>
 #include <program_loading.h>
 
 /* platform_enter_postcar() determines the stack to use after