net/mlx4: Use devl_ API for devlink port register / unregister
Use devl_ API to call devl_port_register() and devl_port_unregister()
instead of devlink_port_register() and devlink_port_unregister(). Add
devlink instance lock in mlx4 driver paths to these functions.
This will be used by the downstream patch to invoke mlx4 devlink reload
callbacks with devlink lock held.