drm/i915: drm_connector_property -> drm_object_property

v2: Rebased.

Signed-off-by: Rob Clark <rob@ti.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com> (v1)
[danvet: Pimp commit message a bit.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>