mlx4: convert to new udp_tunnel_nic infra

Convert to new infra, make use of the ability to sleep in the callback.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Acked-by: Tariq Toukan <tariqt@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>