ip6_tnl_dev_init() sets the dev->iflink via a call to
ip6_tnl_link_config(). After that, register_netdevice()
sets dev->iflink = -1. So we loose the iflink configuration
for ipv6 tunnels. Fix this by using ip6_tnl_dev_init() as the
ndo_init function. Then ip6_tnl_dev_init() is called after
dev->iflink is set to -1 from register_netdevice().
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

(cherry picked from commit 6c6151da)
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>