nb/intel/nehalem/gma: Use common init_igd_opregion method

Use common init_igd_opregion method.

Change-Id: Ic8a85d1373f04814b4460cce377d6e096bcdc349
Signed-off-by: Patrick Rudolph <siro@das-labor.org>
Reviewed-on: https://review.coreboot.org/19907
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Matt DeVillier <matt.devillier@gmail.com>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-by: Martin Roth <martinroth@google.com>
4 files changed