net: remove ndo_udp_tunnel_* callbacks

All UDP tunnel port management is now routed via udp_tunnel_nic
infra directly. Remove the old callbacks.

Reviewed-by: Alexander Duyck <alexanderduyck@fb.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>