arch/x86: Move TSEG_STAGE_CACHE implementation

This is declared weak so that platforms that do not
have smm_subregion() can provide their own implementation.

Change-Id: Ide815b45cbc21a295b8e58434644e82920e84e31
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/34704
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>

src/soc/intel/common/block/smm/smm.c

@@ -22,18 +22,6 @@
 #include <intelblocks/smm.h>
 #include <intelblocks/systemagent.h>
 #include <soc/pm.h>
-#include <stage_cache.h>
-
-#if !CONFIG(PLATFORM_USES_FSP1_1)
-void stage_cache_external_region(void **base, size_t *size)
-{
-	if (smm_subregion(SMM_SUBREGION_CACHE, base, size)) {
-		printk(BIOS_ERR, "ERROR: No cache SMM subregion.\n");
-		*base = NULL;
-		*size = 0;
-	}
-}
-#endif
 
 void smm_southbridge_clear_state(void)
 {