[BRIDGE]: deadlock on device removal

Fixes: https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=131569
Dead lock in bridge when removing device interface module. br_del_if
assumes br->lock not held.

This fixes case of:
	brctl addbr b0
	brctl addif b0 eth0
	rmmod eth0
Signed-off-by: Stephen Hemminger <shemminger@osdl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/bridge/br_notify.c

@@ -76,10 +76,12 @@ static int br_device_event(struct notifier_block *unused, unsigned long event, v
 		break;
 
 	case NETDEV_UNREGISTER:
+		spin_unlock_bh(&br->lock);
 		br_del_if(br, dev);
-		break;
+		goto done;
 	} 
 	spin_unlock_bh(&br->lock);
 
+ done:
 	return NOTIFY_DONE;
 }