net: hns3: remove always exist devlink pointer check

The devlink pointer always exists after hclge_devlink_init() succeed.
Remove that check together with NULL setting after release and ensure
that devlink_register is last command prior to call to devlink_reload_enable().

Fixes: b741269b ("net: hns3: add support for registering devlink for PF")
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>