inet: prepare struct net for TCP MIB accounting

This is the same as the first patch in the set, but preparing
the net for TCP_XXX_STATS - save the struct net on the stack
where required and possible.

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 30dbab7..fc5f716 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -1617,6 +1617,7 @@
 	struct tcphdr *th;
 	struct sock *sk;
 	int ret;
+	struct net *net = dev_net(skb->dev);
 
 	if (skb->pkt_type != PACKET_HOST)
 		goto discard_it;
@@ -1648,7 +1649,7 @@
 	TCP_SKB_CB(skb)->flags = ipv6_get_dsfield(ipv6_hdr(skb));
 	TCP_SKB_CB(skb)->sacked = 0;
 
-	sk = __inet6_lookup(dev_net(skb->dev), &tcp_hashinfo,
+	sk = __inet6_lookup(net, &tcp_hashinfo,
 			&ipv6_hdr(skb)->saddr, th->source,
 			&ipv6_hdr(skb)->daddr, ntohs(th->dest),
 			inet6_iif(skb));