drv/intel/gma/opregion: Add common init_idg_opregion()

Add a new common method to initialize ACPI OpRegion.
* Try to locate vbt.bin in CBFS.
* Try to locate VBIOS in CBFS.
* Keep existing code to probe at 0xc0000.

Tested on Lenovo T430 (sandybridge) using vbt.bin, tested using buggy
VBIOS with wrong vbt_offset, tested with fake vbt written by NGI at
0xc0000.

Tested with https://review.coreboot.org/#/c/21766/ on i945 (using fake
vbt at 0xc0000), x4x (using vbt.bin) and gm45 (using vendor VBIOS).
In all cases linux was successfully provided with VBT from ACPI
opregion.

Change-Id: I8ee50ea9900537bd9e3ca5ab0cd3f48d2acec970
Signed-off-by: Matt DeVillier <matt.devillier@gmail.com>
Signed-off-by: Patrick Rudolph <siro@das-labor.org>
Reviewed-on: https://review.coreboot.org/20969
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
1 file changed