expandable RAID-Z

@@ -89,8 +89,9 @@
         vdev_missing_probe,
         vdev_default_asize,
         vdev_missing_io_start,
         vdev_missing_io_done,
         NULL,
+        NULL,
         VDEV_TYPE_MISSING,      /* name of this vdev type */
         B_TRUE                  /* leaf vdev */
 };