drm: Automatically unregister the connector during cleanup

As we now can call drm_connector_unregister() multiple times, provide a
failsafe unregister for a connector when cleaning it up.

v2: Add a WARN to catch any connectors that are still visible to
userspace when we come to destoy them.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Dave Airlie <airlied@redhat.com>
Cc: dri-devel@lists.freedesktop.org
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1465993109-19523-5-git-send-email-chris@chris-wilson.co.uk

drivers/gpu/drm/drm_crtc.c

@@ -938,6 +938,12 @@ void drm_connector_cleanup(struct drm_connector *connector)
 	struct drm_device *dev = connector->dev;
 	struct drm_display_mode *mode, *t;
 
+	/* The connector should have been removed from userspace long before
+	 * it is finally destroyed.
+	 */
+	if (WARN_ON(connector->registered))
+		drm_connector_unregister(connector);
+
 	if (connector->tile_group) {
 		drm_mode_put_tile_group(dev, connector->tile_group);
 		connector->tile_group = NULL;