Merge branch 'backlight-rework' into drm-intel-next-queued

Pull in Jani's backlight rework branch. This was merged through a
separate branch to be able to sort out the Broadwell conflicts
properly before pulling it into the main development branch.

Conflicts:
	drivers/gpu/drm/i915/intel_display.c

Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>