tuntap: remove unnecessary sk_receive_queue length check during xmit

After commit 1576d986 ("tun: switch to use skb array for tx"),
sk_receive_queue was not used any more. So remove the uncessary
sk_receive_queue length check during xmit.
Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/tun.c

@@ -878,13 +878,6 @@ static netdev_tx_t tun_net_xmit(struct sk_buff *skb, struct net_device *dev)
 	    sk_filter(tfile->socket.sk, skb))
 		goto drop;
 
-	/* Limit the number of packets queued by dividing txq length with the
-	 * number of queues.
-	 */
-	if (skb_queue_len(&tfile->socket.sk->sk_receive_queue) * numqueues
-			  >= dev->tx_queue_len)
-		goto drop;
-
 	if (unlikely(skb_orphan_frags(skb, GFP_ATOMIC)))
 		goto drop;