drm/i915: add opregion function to notify bios of adapter power state

Notifying the bios lets it enter power saving states.

Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
2 files changed