nb/x4x: Do not enable IGD when not supported

According to "Intel ® 4 Series Chipset Family datasheet" in the
description about GGC and DEVEN, CAPID0 bit46 is said to reflect the
presence of an internal graphic device. This would allow the P43 and
P45 chipset variants to work.

Change-Id: Icdaa2862f82000de6d51278098365c63b7719f7f
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/18515
Reviewed-by: Nico Huber <nico.h@gmx.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
1 file changed