northbridge/sandybridge/raminit_mrc.c: fix missing include

Compilation (w/o native raminit) fails due to missing include

Change-Id: Ic79a77006257b32e0181c88c4e24d7c1f5c5f7ce
Signed-off-by: Matt DeVillier <matt.devillier@gmail.com>
Reviewed-on: https://review.coreboot.org/16735
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <pgeorgi@google.com>

src/northbridge/intel/sandybridge/raminit_mrc.c

@@ -30,6 +30,7 @@
 #include "raminit.h"
 #include "pei_data.h"
 #include "sandybridge.h"
+#include <vboot/vboot_common.h>
 
 /* Management Engine is in the southbridge */
 #include "southbridge/intel/bd82x6x/me.h"