drm: add support for private planes

In cases where the scanout hw is sufficiently similar between "overlay"
and traditional crtc layers, it might be convenient to allow the driver
to create internal drm_plane helper objects used by the drm_crtc
implementation, rather than duplicate code between the plane and crtc.
A private plane is not exposed to userspace.

Signed-off-by: Rob Clark <rob@ti.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
index 2deb6f9..63e4fce 100644
--- a/include/drm/drm_crtc.h
+++ b/include/drm/drm_crtc.h
@@ -829,7 +829,8 @@
 			  struct drm_plane *plane,
 			  unsigned long possible_crtcs,
 			  const struct drm_plane_funcs *funcs,
-			  const uint32_t *formats, uint32_t format_count);
+			  const uint32_t *formats, uint32_t format_count,
+			  bool priv);
 extern void drm_plane_cleanup(struct drm_plane *plane);
 
 extern void drm_encoder_cleanup(struct drm_encoder *encoder);