net: hns3: add client node validity judgment

HNS3 driver can only unregister client which included in hnae3_client_list.
This patch adds the client node validity judgment.

Signed-off-by: Peng Li <lipeng321@huawei.com>
Signed-off-by: Huazhong Tan <tanhuazhong@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>