netfilter: ip6tables: add MASQUERADE target

Signed-off-by: Patrick McHardy <kaber@trash.net>
diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index e581009..19d4bff 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -1093,7 +1093,7 @@
 	return ret;
 }
 
-int ipv6_dev_get_saddr(struct net *net, struct net_device *dst_dev,
+int ipv6_dev_get_saddr(struct net *net, const struct net_device *dst_dev,
 		       const struct in6_addr *daddr, unsigned int prefs,
 		       struct in6_addr *saddr)
 {