[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/include/net/ip6_route.h b/include/net/ip6_route.h
index 9080076..9313491 100644
--- a/include/net/ip6_route.h
+++ b/include/net/ip6_route.h
@@ -61,13 +61,13 @@
 extern int			ip6_del_rt(struct rt6_info *);
 
 extern struct rt6_info		*rt6_lookup(struct net *net,
-					    struct in6_addr *daddr,
-					    struct in6_addr *saddr,
+					    const struct in6_addr *daddr,
+					    const struct in6_addr *saddr,
 					    int oif, int flags);
 
 extern struct dst_entry *icmp6_dst_alloc(struct net_device *dev,
 					 struct neighbour *neigh,
-					 struct in6_addr *addr);
+					 const struct in6_addr *addr);
 extern int icmp6_dst_gc(int *more);
 
 extern void fib6_force_start_gc(struct net *net);