cxgb4: convert to new udp_tunnel_nic infra

Convert to new infra, this driver is very simple. The check of
adapter->rawf_cnt in cxgb_udp_tunnel_unset_port() is kept from
the old port deletion function but it's dodgy since nothing ever
updates that member once its set during init. Also .set_port
callback always adds the raw mac filter..

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>