[NETFILTER]: NAT: silence unused variable warnings with CONFIG_XFRM=n

net/ipv4/netfilter/ip_nat_standalone.c: In function 'ip_nat_out':
net/ipv4/netfilter/ip_nat_standalone.c:223: warning: unused variable 'ctinfo'
net/ipv4/netfilter/ip_nat_standalone.c:222: warning: unused variable 'ct'

Surprisingly no complaints so far ..
Signed-off-by: NPatrick McHardy <kaber@trash.net>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv4/netfilter/ip_nat_standalone.c

@@ -219,8 +219,10 @@ ip_nat_out(unsigned int hooknum,
 	   const struct net_device *out,
 	   int (*okfn)(struct sk_buff *))
 {
+#ifdef CONFIG_XFRM
 	struct ip_conntrack *ct;
 	enum ip_conntrack_info ctinfo;
+#endif
 	unsigned int ret;
 
 	/* root is playing with raw sockets. */