drm/plane-helper: Adapt cursor hack to transitional helpers

In

commit f02ad907cd9e7fe3a6405d2d005840912f1ed258
Author: Daniel Vetter <daniel.vetter@ffwll.ch>
Date:   Thu Jan 22 16:36:23 2015 +0100

    drm/atomic-helpers: Recover full cursor plane behaviour

we've added a hack to atomic helpers to never to vblank waits for
cursor updates through the legacy apis since that's what X expects.
Unfortunately we've (again) forgotten to adjust the transitional
helpers. Do this now.

This fixes regressions for drivers only partially converted over to
atomic (like i915).

Reported-by: Pekka Paalanen <ppaalanen@gmail.com>
Cc: Pekka Paalanen <ppaalanen@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Reviewed-and-tested-by: Mario Kleiner <mario.kleiner.de@gmail.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>

drivers/gpu/drm/drm_plane_helper.c

@@ -465,6 +465,9 @@ int drm_plane_helper_commit(struct drm_plane *plane,
 		if (!crtc[i])
 			continue;
 
+		if (crtc[i]->cursor == plane)
+			continue;
+
 		/* There's no other way to figure out whether the crtc is running. */
 		ret = drm_crtc_vblank_get(crtc[i]);
 		if (ret == 0) {