lib/prog_loaders: use common ramstage_cache_invalid()

All current implementations of ramstage_cache_invalid() were just
resetting the system based on the RESET_ON_INVALID_RAMSTAGE_CACHE
Kconfig option. Move that behavior to a single implementation
within prog_loaders.c which removes duplication.

Change-Id: I67aae73f9e1305732f90d947fe57c5aaf66ada9e
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://review.coreboot.org/17184
Tested-by: build bot (Jenkins)
Reviewed-by: Duncan Laurie <dlaurie@chromium.org>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Furquan Shaikh <furquan@google.com>

src/drivers/intel/fsp2_0/stage_cache.c

@@ -28,10 +28,3 @@ void stage_cache_external_region(void **base, size_t *size)
 		*size = 0;
 	}
 }
-
-void ramstage_cache_invalid(void)
-{
-	if (IS_ENABLED(CONFIG_RESET_ON_INVALID_RAMSTAGE_CACHE))
-		/* Perform cold reset on invalid ramstage cache. */
-		hard_reset();
-}