em_meta: avoid one dev_put()

Another rcu conversion to avoid one dev_hold()/dev_put() pair
Signed-off-by: NEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/sched/em_meta.c

@@ -309,10 +309,10 @@ META_COLLECTOR(var_sk_bound_if)
 	} else {
 		struct net_device *dev;
 
-		dev = dev_get_by_index(&init_net, skb->sk->sk_bound_dev_if);
+		rcu_read_lock();
+		dev = dev_get_by_index_rcu(&init_net, skb->sk->sk_bound_dev_if);
 		*err = var_dev(dev, dst);
-		if (dev)
-			dev_put(dev);
+		rcu_read_unlock();
 	}
 }