IFLA_IPTUN_LOCAL and IFLA_IPTUN_REMOTE were inverted.

Introduced by c075b130 (ip6tnl: advertise tunnel param via rtnl).
Signed-off-by: NDing Zhi <zhi.ding@6wind.com>
Signed-off-by: NNicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>