net: switchdev: Add extack to switchdev_handle_port_obj_add() callback

Drivers use switchdev_handle_port_obj_add() to handle recursive descent
through lower devices. Change this function prototype to take add_cb
that itself takes an extack argument. Decode extack from
switchdev_notifier_port_obj_info and pass it to add_cb.

Update mlxsw and ocelot drivers which use this helper.

Signed-off-by: Petr Machata <petrm@mellanox.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Acked-by: Ivan Vecera <ivecera@redhat.com>
Reviewed-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>