net/sched: act_tunnel_key: Fix setting UDP dst port in metadata under IPv6

The UDP dst port was provided to the helper function which sets the
IPv6 IP tunnel meta-data under a wrong param order, fix that.

Fixes: 75bfbca0 ('net/sched: act_tunnel_key: Add UDP dst port option')
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Reviewed-by: Hadar Hen Zion <hadarh@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>