net: hns3: stop mailbox handling when command queue need re-init

If the command queue needs re-initialization, the mailbox handling
task should do nothing, otherwise this task will just get some error
print.

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