[TCP]: Restore SKB socket owner setting in tcp_transmit_skb().

Revert 931731123a103cfb3f70ac4b7abfc71d94ba1f03

We can't elide the skb_set_owner_w() here because things like certain
netfilter targets (such as owner MATCH) need a socket to be set on the
SKB for correct operation.

Thanks to Jan Engelhardt and other netfilter list members for
pointing this out.

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 c700302..116f94a 100644
--- a/net/ipv6/inet6_connection_sock.c
+++ b/net/ipv6/inet6_connection_sock.c
@@ -139,8 +139,9 @@
 
 EXPORT_SYMBOL_GPL(inet6_csk_addr2sockaddr);
 
-int inet6_csk_xmit(struct sk_buff *skb, struct sock *sk, int ipfragok)
+int inet6_csk_xmit(struct sk_buff *skb, int ipfragok)
 {
+	struct sock *sk = skb->sk;
 	struct inet_sock *inet = inet_sk(sk);
 	struct ipv6_pinfo *np = inet6_sk(sk);
 	struct flowi fl;