drm/plane: Pass old state to ->atomic_update()

In most situations it will be useful to have the old state passed to the
->atomic_update() callback. For example if a plane is being disabled the
new state's .crtc field will be NULL, but some drivers may rely on this
field to program the CRTCs registers.

v2: rename variable to old_plane_state and remove redundant comment as
suggested by Daniel Vetter, remove an Exynos hunk that doesn't apply to
drm-next and add a hunk for pending MSM mdp5 changes

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/include/drm/drm_plane_helper.h b/include/drm/drm_plane_helper.h
index c48f14d..fcfa969 100644
--- a/include/drm/drm_plane_helper.h
+++ b/include/drm/drm_plane_helper.h
@@ -60,7 +60,8 @@
 
 	int (*atomic_check)(struct drm_plane *plane,
 			    struct drm_plane_state *state);
-	void (*atomic_update)(struct drm_plane *plane);
+	void (*atomic_update)(struct drm_plane *plane,
+			      struct drm_plane_state *old_state);
 };
 
 static inline void drm_plane_helper_add(struct drm_plane *plane,