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>
1 file changed