google/butterfly: add function needed for MRC raminit

All other Sandy/IvyBridge google boards have this function,
which is required by nb/sandybridge/raminit_mrc.c. Without it,
compilation fails when using MRC vs native ram init.

Change-Id: I3318700c540e97baf0a75aafb73f160aaae6703f
Signed-off-by: Matt DeVillier <matt.devillier@gmail.com>
Reviewed-on: https://review.coreboot.org/20538
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>

src/mainboard/google/butterfly/romstage.c

@@ -188,3 +188,8 @@ void mainboard_fill_pei_data(struct pei_data *pei_data)
 	};
 	*pei_data = pei_data_template;
 }
+
+int mainboard_should_reset_usb(int s3resume)
+{
+	return !s3resume;
+}