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
1 file changed