netdev: add rcu annotations to receive handler hook

Suggested by Eric's bridge RCU changes.
Signed-off-by: NStephen Hemminger <shemminger@vyatta.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

include/linux/netdevice.h

@@ -994,8 +994,8 @@ struct net_device {
 	unsigned int		real_num_rx_queues;
 #endif
 
-	rx_handler_func_t	*rx_handler;
-	void			*rx_handler_data;
+	rx_handler_func_t __rcu	*rx_handler;
+	void __rcu		*rx_handler_data;
 
 	struct netdev_queue __rcu *ingress_queue;