[NETFILTER]: Export ip_nat_port_{nfattr_to_range,range_to_nfattr}

Those exports are needed by the PPTP helper following in the next
couple of changes.
Signed-off-by: Harald Welte <laforge@netfilter.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/netfilter/ip_nat_core.c

@@ -578,6 +578,8 @@ ip_nat_port_nfattr_to_range(struct nfattr *tb[], struct ip_nat_range *range)
 
 	return ret;
 }
+EXPORT_SYMBOL_GPL(ip_nat_port_nfattr_to_range);
+EXPORT_SYMBOL_GPL(ip_nat_port_range_to_nfattr);
 #endif
 
 int __init ip_nat_init(void)