[Intel-gfx] Small series to enable OpRegion->VBT

[Chris Wilson]

This looks to be a useful set of patches that enable VBT parsing on
machines with only a compressed VBIOS and so provide fixed-panel modes
for my netbooks. In conjunction with this, I then hit an issue where the
BIOS writers became creative in their use of VBT and so I needed a small
patch to lvds_is_present_in_vbt() to account for the new brain damage.
After Adam's insight, we just accept the VBT without question if it came
from OpRegion.