[NETPOLL]: deadlock bugfix

This fixes an obvious deadlock in the netpoll code.  netpoll_rx takes the
npinfo->rx_lock.  netpoll_rx is also the only caller of arp_reply (through
__netpoll_rx).  As such, it is not necessary to take this lock.
Signed-off-by: NJeff Moyer <jmoyer@redhat.com>
Signed-off-by: NMatt Mackall <mpm@selenic.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/core/netpoll.c

@@ -353,11 +353,8 @@ static void arp_reply(struct sk_buff *skb)
 	struct sk_buff *send_skb;
 	struct netpoll *np = NULL;
 
-	spin_lock_irqsave(&npinfo->rx_lock, flags);
 	if (npinfo->rx_np && npinfo->rx_np->dev == skb->dev)
 		np = npinfo->rx_np;
-	spin_unlock_irqrestore(&npinfo->rx_lock, flags);
-
 	if (!np)
 		return;