[hermon] Stop firmware only once on shutdown

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/drivers/infiniband/hermon.c

 	hermon_cmd_close_hca ( hermon );
 	hermon_free_icm ( hermon );
 	hermon_stop_firmware ( hermon );
-	hermon_stop_firmware ( hermon );
 	for ( i = ( hermon->cap.num_ports - 1 ) ; i >= 0 ; i-- ) {
 		netdev_nullify ( hermon->port[i].netdev );
 		netdev_put ( hermon->port[i].netdev );