fix compilation of intel/sch northbridge code with gcc 4.6

fix compilation of intel/sch northbridge code with gcc 4.6

Change-Id: I57804dff9e37f0127900ebb7a67118382944eb89
Signed-off-by: Stefan Reinauer <reinauer@google.com>
Reviewed-on: http://review.coreboot.org/264
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <patrick@georgi-clan.de>