Since addrconf_add_dev() has already called addrconf_add_mroute()
to added route for multicast prefix, there's no point to call it
again in addrconf_ip6_tnl_config().
Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org> Signed-off-by: David S. Miller <davem@davemloft.net>