drm/virtio: add missing drm_atomic_helper_shutdown() call.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20190401140306.28063-2-kraxel@redhat.com

drivers/gpu/drm/virtio/virtgpu_display.c

@@ -385,5 +385,6 @@ void virtio_gpu_modeset_fini(struct virtio_gpu_device *vgdev)
 
 	for (i = 0 ; i < vgdev->num_scanouts; ++i)
 		kfree(vgdev->outputs[i].edid);
+	drm_atomic_helper_shutdown(vgdev->ddev);
 	drm_mode_config_cleanup(vgdev->ddev);
 }