gma500: Fix oaktrail probing part 1

The Oaktrail platform does not use the GCT/VBT format that is used by the
Moorestowm (non PC legacy) equivalent device. It uses the BIOS tables which
means an opregion and the like.

The current code uses the wrong table which breaks things like the Fujitsu
q550 tablets. Fix the table usage as a first step.

The problem was found and diagnosed by Chia-I Wu

Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>