Set up IGD OpRegion in northbridge and fill in GNVS' aslb.
At this point GNVS already has been set up by SSDT injection.
Required for future VBT patches that will:
* Use ACPI memory instead of CBMEM
* Use common implementation to locate VBT
* Fill in platform specific values
Change-Id: I76b31fe5fd19b50b82f57748558fb04408e0fd23
Signed-off-by: Patrick Rudolph <siro@das-labor.org>
Reviewed-on: https://review.coreboot.org/19309
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@chromium.org>