[TCP]: Don't set SKB owner in tcp_transmit_skb().

The data itself is already charged to the SKB, doing
the skb_set_owner_w() just generates a lot of noise and
extra atomics we don't really need.

Lmbench improvements on lat_tcp are minimal:

before:
TCP latency using localhost: 23.2701 microseconds
TCP latency using localhost: 23.1994 microseconds
TCP latency using localhost: 23.2257 microseconds

after:
TCP latency using localhost: 22.8380 microseconds
TCP latency using localhost: 22.9465 microseconds
TCP latency using localhost: 22.8462 microseconds

Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/inet6_connection_sock.c b/net/ipv6/inet6_connection_sock.c
index e48fb4c..c598962 100644
--- a/net/ipv6/inet6_connection_sock.c
+++ b/net/ipv6/inet6_connection_sock.c
@@ -139,9 +139,8 @@
 
 EXPORT_SYMBOL_GPL(inet6_csk_addr2sockaddr);
 
-int inet6_csk_xmit(struct sk_buff *skb, int ipfragok)
+int inet6_csk_xmit(struct sk_buff *skb, struct sock *sk, int ipfragok)
 {
-	struct sock *sk = skb->sk;
 	struct inet_sock *inet = inet_sk(sk);
 	struct ipv6_pinfo *np = inet6_sk(sk);
 	struct flowi fl;