Since cbfs_core.h provides a macro that uses ntohl, make sure ntohl is available

Since cbfs_core.h provides a macro that uses ntohl, make sure ntohl is available

Since cbfs_core.h provides a macro that uses ntohl, make sure ntohl is available by
including byteorder.h

Change-Id: I9ab8cb51bd680e861b28d5130d09547bb9ab3b1f
Signed-off-by: Gabe Black <gabeblack@google.com>
Reviewed-on: http://review.coreboot.org/709
Tested-by: build bot (Jenkins)
Reviewed-by: Peter Stuge <peter@stuge.se>