drm/i915: Wait for vblank between disabling a sprite and unpinning the fb

When disabling a sprite, wait for the sprite to stop fetching data
from memory before unpinning the fb.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_sprite.c

@@ -582,6 +582,8 @@ intel_disable_plane(struct drm_plane *plane)
 	if (!intel_plane->obj)
 		goto out;
 
+	intel_wait_for_vblank(dev, intel_plane->pipe);
+
 	mutex_lock(&dev->struct_mutex);
 	intel_unpin_fb_obj(intel_plane->obj);
 	intel_plane->obj = NULL;