netfilter: nf_ct_tcp: fix up build after merge

Replace the last occurence of tcp_lock by the per-conntrack lock.

Signed-off-by: Patrick McHardy <kaber@trash.net>
diff --git a/net/netfilter/nf_conntrack_proto_tcp.c b/net/netfilter/nf_conntrack_proto_tcp.c
index 5142e60..33fc0a4 100644
--- a/net/netfilter/nf_conntrack_proto_tcp.c
+++ b/net/netfilter/nf_conntrack_proto_tcp.c
@@ -944,7 +944,7 @@
 		    && (ct->proto.tcp.seen[!dir].flags & IP_CT_TCP_FLAG_MAXACK_SET)
 		    && before(ntohl(th->seq), ct->proto.tcp.seen[!dir].td_maxack)) {
 			/* Invalid RST  */
-			write_unlock_bh(&tcp_lock);
+			spin_unlock_bh(&ct->lock);
 			if (LOG_INVALID(net, IPPROTO_TCP))
 				nf_log_packet(pf, 0, skb, NULL, NULL, NULL,
 					  "nf_ct_tcp: invalid RST ");