netfilter: Fix SIP conntrack build with NAT disabled.

Reported by Ingo Molnar.

The SIP helper is also useful without NAT. This patch adds an ifdef
around the RTP call optimization for NATed clients.
Signed-off-by: NPatrick McHardy <kaber@trash.net>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/netfilter/nf_conntrack_sip.c

@@ -781,7 +781,7 @@ static int set_expected_rtp_rtcp(struct sk_buff *skb,
 		    nfct_help(exp->master)->helper != nfct_help(ct)->helper ||
 		    exp->class != class)
 			break;
-
+#ifdef CONFIG_NF_NAT_NEEDED
 		if (exp->tuple.src.l3num == AF_INET && !direct_rtp &&
 		    (exp->saved_ip != exp->tuple.dst.u3.ip ||
 		     exp->saved_proto.udp.port != exp->tuple.dst.u.udp.port) &&
@@ -791,6 +791,7 @@ static int set_expected_rtp_rtcp(struct sk_buff *skb,
 			tuple.dst.u.udp.port	= exp->saved_proto.udp.port;
 			direct_rtp = 1;
 		} else
+#endif
 			skip_expect = 1;
 	} while (!skip_expect);
 	rcu_read_unlock();