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>
diff --git a/drivers/gpu/drm/i915/intel_sprite.c b/drivers/gpu/drm/i915/intel_sprite.c
index 414d325..27df5b8 100644
--- a/drivers/gpu/drm/i915/intel_sprite.c
+++ b/drivers/gpu/drm/i915/intel_sprite.c
@@ -582,6 +582,8 @@
 	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;