mlxsw: spectrum_ipip: Handle underlay device change

When a bound device of an IP-in-IP tunnel changes, such as through
'ip tunnel change name $name dev $dev', the loopback backing the tunnel
needs to be recreated.

Signed-off-by: Petr Machata <petrm@mellanox.com>
Reviewed-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>