stage_cache: Add resume_from_stage_cache()

Factor out the condition when an attempt to load
stage from cache can be tried.

Change-Id: I936f07bed6fc82f46118d217f1fd233e2e041405
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/50000
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>

src/arch/x86/postcar_loader.c

@@ -9,7 +9,6 @@
 #include <program_loading.h>
 #include <reset.h>
 #include <rmodule.h>
-#include <romstage_handoff.h>
 #include <stage_cache.h>
 #include <timestamp.h>
 #include <security/vboot/vboot_common.h>
@@ -183,8 +182,7 @@ void run_postcar_phase(struct postcar_frame *pcf)
 
 	postcar_commit_mtrrs(pcf);
 
-	if (!CONFIG(NO_STAGE_CACHE) &&
-				romstage_handoff_is_resume()) {
+	if (resume_from_stage_cache()) {
 		stage_cache_load_stage(STAGE_POSTCAR, &prog);
 		/* This is here to allow platforms to pass different stack
 		   parameters between S3 resume and normal boot. On the