[IPV6]: Make address arguments const.

- net/ipv6/addrconf.c:
	ipv6_get_ifaddr(), ipv6_dev_get_saddr()
- net/ipv6/mcast.c:
	ipv6_sock_mc_join(), ipv6_sock_mc_drop(),
	inet6_mc_check(),
	ipv6_dev_mc_inc(), __ipv6_dev_mc_dec(), ipv6_dev_mc_dec(),
	ipv6_chk_mcast_addr()
- net/ipv6/route.c:
	rt6_lookup(), icmp6_dst_alloc()
- net/ipv6/ip6_output.c:
	ip6_nd_hdr()
- net/ipv6/ndisc.c:
	ndisc_send_ns(), ndisc_send_rs(), ndisc_send_redirect(),
	ndisc_get_neigh(), __ndisc_send()

Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index d15f3e0..4048c2b 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -940,7 +940,7 @@
 };
 
 struct ipv6_saddr_dst {
-	struct in6_addr *addr;
+	const struct in6_addr *addr;
 	int ifindex;
 	int scope;
 	int label;
@@ -1074,7 +1074,7 @@
 }
 
 int ipv6_dev_get_saddr(struct net_device *dst_dev,
-		       struct in6_addr *daddr, unsigned int prefs,
+		       const struct in6_addr *daddr, unsigned int prefs,
 		       struct in6_addr *saddr)
 {
 	struct ipv6_saddr_score scores[2],
@@ -1309,7 +1309,7 @@
 
 EXPORT_SYMBOL(ipv6_chk_prefix);
 
-struct inet6_ifaddr *ipv6_get_ifaddr(struct net *net, struct in6_addr *addr,
+struct inet6_ifaddr *ipv6_get_ifaddr(struct net *net, const struct in6_addr *addr,
 				     struct net_device *dev, int strict)
 {
 	struct inet6_ifaddr * ifp;