use rc.common for usb init script

SVN-Revision: 6873

package/base-files/files/etc/init.d/usb

@@ -1,6 +1,6 @@
-#!/bin/sh
+#!/bin/sh /etc/rc.common
 # Copyright (C) 2006 OpenWrt.org 
-#
+
 START=39
 start() {
 	[ -d /proc/bus/usb ] && {