nfnetlink_queue: Use rcu_barrier() on module unload.

This module uses rcu_call() thus it should use rcu_barrier() on module unload.

Also fixed a trivial typo 'nfetlink' -> 'nfnetlink' in comment.
Signed-off-by: NJesper Dangaard Brouer <hawk@comx.dk>
Acked-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: NPatrick McHardy <kaber@trash.net>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/netfilter/nfnetlink_queue.c

 /*
  * This is a module which is used for queueing packets and communicating with
- * userspace via nfetlink.
+ * userspace via nfnetlink.
  *
  * (C) 2005 by Harald Welte <laforge@netfilter.org>
  * (C) 2007 by Patrick McHardy <kaber@trash.net>
@@ -932,6 +932,8 @@ static void __exit nfnetlink_queue_fini(void)
 #endif
 	nfnetlink_subsys_unregister(&nfqnl_subsys);
 	netlink_unregister_notifier(&nfqnl_rtnl_notifier);
+
+	rcu_barrier(); /* Wait for completion of call_rcu()'s */
 }
 
 MODULE_DESCRIPTION("netfilter packet queue handler");