soc/intel/braswell/acpi: Clean OpRegion up

Reorder code and put platform specific bits into update_igd_opregion.
Get rid of get_fsp_vbt and init_igd_opregion.
Write GMA opregion in case a VBT was provided, even when no FSP_GOP
is to be run.
Use SOC_INTEL_COMMON_GFX_OPREGION to reduce code duplication.

Change-Id: Ibabeb05a9d3d776b73f6885dcca846d5001116e7
Signed-off-by: Patrick Rudolph <siro@das-labor.org>
Reviewed-on: https://review.coreboot.org/20221
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Matt DeVillier <matt.devillier@gmail.com>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
3 files changed