drm: Add plane type property (v2)

Add a plane type property to allow userspace to distinguish plane types.

v2: Driver-specific churn eliminated now that drm_plane_init() and
    drm_universal_plane_init() were separated out in a previous patch.

Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Rob Clark <robdclark@gmail.com>
diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
index 201d8c2..4c4f792 100644
--- a/include/drm/drm_crtc.h
+++ b/include/drm/drm_crtc.h
@@ -771,6 +771,7 @@
 	struct list_head property_blob_list;
 	struct drm_property *edid_property;
 	struct drm_property *dpms_property;
+	struct drm_property *plane_type_property;
 
 	/* DVI-I properties */
 	struct drm_property *dvi_i_subconnector_property;