nb/intel/sandybridge: add pch.h include

Fixes src/northbridge/intel/sandybridge/raminit_mrc.c:286:3: error:
implicit declaration of function 'enable_usb_bar'

Change-Id: I48bf59c56b518477a3fc0d75902fc58df6b7def7
Signed-off-by: Patrick Georgi <pgeorgi@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/32400
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-by: Patrick Rudolph <siro@das-labor.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/northbridge/intel/sandybridge/raminit_mrc.c

@@ -33,6 +33,7 @@
 #include "pei_data.h"
 #include "sandybridge.h"
 #include <security/vboot/vboot_common.h>
+#include <southbridge/intel/bd82x6x/pch.h>
 
 /* Management Engine is in the southbridge */
 #include <southbridge/intel/bd82x6x/me.h>