i40e: convert to new udp_tunnel infrastructure

Make use of the "shared port table" to convert i40e to the new
infra.

i40e did not have any reference tracking, locking is also dodgy
because rtnl gets released while talking to FW, so port may get
removed from the table while it's getting added etc.

On the good side i40e does not seem to be using the ports for
TX so we can remove the table from the driver state completely.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>