drivers/intel/gma: Include mainboard data.vbt

This adds a INTEL_GMA_VBT_HAVE_DATA_FILE Kconfig option for the path
to point to the mainboard dir and to select
INTEL_GMA_ADD_VBT_DATA_FILE by default.

Change-Id: I730cb0737945631e2d5379a9e26b8c039ec6dc49
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/26653
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Nico Huber <nico.h@gmx.de>
9 files changed