drm: disconnect plane from fb/crtc when disabled

Since plane->fb and plane->crtc are set in drm_mode_setplane()
after update_plane(), They should be cleared after disable().

Signed-off-by: Rob Clark <rob@ti.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/drm_crtc.c

@@ -348,6 +348,9 @@ void drm_framebuffer_cleanup(struct drm_framebuffer *fb)
 			ret = plane->funcs->disable_plane(plane);
 			if (ret)
 				DRM_ERROR("failed to disable plane with busy fb\n");
+			/* disconnect the plane from the fb and crtc: */
+			plane->fb = NULL;
+			plane->crtc = NULL;
 		}
 	}