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/soc/intel/braswell/memmap.c b/src/soc/intel/braswell/memmap.c
index a4692ce..69bbe58 100644
--- a/src/soc/intel/braswell/memmap.c
+++ b/src/soc/intel/braswell/memmap.c
@@ -15,7 +15,7 @@
  */
 
 #include <cbmem.h>
-#include <fsp/memmap.h>
+#include <cpu/x86/smm.h>
 #include <soc/iosf.h>
 #include <soc/smm.h>