[TCP]: Fix unlikely usage in tcp_transmit_skb()

The following unlikely should be replaced by likely because the
condition happens every time unless there is a hard error to transmit
a packet.
Signed-off-by: NHua Zhong <hzhong@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv4/tcp_output.c

@@ -465,7 +465,7 @@ static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it,
 	TCP_INC_STATS(TCP_MIB_OUTSEGS);
 
 	err = icsk->icsk_af_ops->queue_xmit(skb, 0);
-	if (unlikely(err <= 0))
+	if (likely(err <= 0))
 		return err;
 
 	tcp_enter_cwr(sk);