Make Geode GX2 VGA setup work.

Make Geode GX2 VGA setup work.

Add MSR register write for VGA memory setup
Add missing license
Add bit explanation

Change-Id: I1cb36eeccd84f0056c829f50d9864047654ce906
Signed-off-by: Nils Jacobs <njacobs8@adsltotaal.nl>
Reviewed-on: http://review.coreboot.org/580
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>