net: hns3: add waiting time before cmdq memory is released

driver inclusion
category: bugfix
bugzilla: NA
CVE: NA

----------------------------

After the cmdq registers are cleared, the firmware may take time to
clear out possible left over commands in the cmdq. Driver must release
cmdq memory only after firmware has completed processing of left over
commands.

Signed-off-by: Yufeng Mo <moyufeng@huawei.com>
Signed-off-by: Yonglong Liu <liuyonglong@huawei.com>
Reviewed-by: li yongxin <liyongxin1@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>