netfilter: Fix warning in nfnetlink_receive().

net/netfilter/nfnetlink.c: In function ‘nfnetlink_rcv’:
net/netfilter/nfnetlink.c:371:14: warning: unused variable ‘net’ [-Wunused-variable]
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/netfilter/nfnetlink.c

@@ -368,7 +368,6 @@ static void nfnetlink_rcv_batch(struct sk_buff *skb, struct nlmsghdr *nlh,
 static void nfnetlink_rcv(struct sk_buff *skb)
 {
 	struct nlmsghdr *nlh = nlmsg_hdr(skb);
-	struct net *net = sock_net(skb->sk);
 	int msglen;
 
 	if (nlh->nlmsg_len < NLMSG_HDRLEN ||