In order to remove complexity in devlink core related to
devlink_reload_enable/disable, let's rewrite new_port/del_port
logic to rely on internal to netdevsim lcok.

We should protect only reload_down flow because it destroys nsim_dev,
which is needed for nsim_dev_port_add/nsim_dev_port_del to hold
port_list_lock.
Signed-off-by: NLeon Romanovsky <leonro@nvidia.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>