nb/intel: Use postcar_frame_add_romcache()

Change-Id: I0729ca4cdad7d2218c1e1feae5cd38dda6d4e11e
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/26579
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
diff --git a/src/northbridge/intel/sandybridge/ram_calc.c b/src/northbridge/intel/sandybridge/ram_calc.c
index c76e4be..cf583c03 100644
--- a/src/northbridge/intel/sandybridge/ram_calc.c
+++ b/src/northbridge/intel/sandybridge/ram_calc.c
@@ -57,8 +57,7 @@
 		die("Unable to initialize postcar frame.\n");
 
 	/* Cache the ROM as WP just below 4GiB. */
-	postcar_frame_add_mtrr(&pcf, CACHE_ROM_BASE, CACHE_ROM_SIZE,
-		MTRR_TYPE_WRPROT);
+	postcar_frame_add_romcache(&pcf, MTRR_TYPE_WRPROT);
 
 	/* Cache RAM as WB from 0 -> CACHE_TMP_RAMTOP. */
 	postcar_frame_add_mtrr(&pcf, 0, CACHE_TMP_RAMTOP, MTRR_TYPE_WRBACK);