drm/atomic-helper: Really recover pre-atomic plane/cursor behavior

I've fumbled this in

commit f02ad907
Author: Daniel Vetter <daniel.vetter@ffwll.ch>
Date:   Thu Jan 22 16:36:23 2015 +0100

    drm/atomic-helpers: Recover full cursor plane behaviour

and accidentally put the assignment for legacy_cursor_upate after the
atomic commit, where it is pretty useless.
Reported-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>

drivers/gpu/drm/drm_atomic_helper.c

@@ -1310,13 +1310,13 @@ int drm_atomic_helper_update_plane(struct drm_plane *plane,
 	plane_state->src_h = src_h;
 	plane_state->src_w = src_w;
 
+	if (plane == crtc->cursor)
+		state->legacy_cursor_update = true;
+
 	ret = drm_atomic_commit(state);
 	if (ret != 0)
 		goto fail;
 
-	if (plane == crtc->cursor)
-		state->legacy_cursor_update = true;
-
 	/* Driver takes ownership of state on successful commit. */
 	return 0;
 fail: