soc/intel/common/opregion: Get rid of opregion.c

soc/intel/common/opregion: Get rid of opregion.c

Get rid of custom opregion implementation and use drivers/intel/gma/opregion
implementation instead.

Test: boot Windows 10 on google/chell and google/edgar using Tianocore
payload with GOP init, observe Intel graphics driver loaded and functional.

Change-Id: I5f78e9030df12da5369d142dda5c59e576ebcef7
Signed-off-by: Patrick Rudolph <siro@das-labor.org>
Signed-off-by: Matt DeVillier <matt.devillier@gmail.com>
Reviewed-on: https://review.coreboot.org/21703
Reviewed-by: Nico Huber <nico.h@gmx.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>