net: hns3: clear command queue's registers when unloading VF driver

According to the hardware's description, the driver should clear
the command queue's registers when uloading VF driver. Otherwise,
these existing value may lead the IMP get into a wrong state.

Fixes: fedd0c15

 ("net: hns3: Add HNS3 VF IMP(Integrated Management Proc) cmd interface")
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>