net/hns3: fix VF reset on mailbox failure

net/hns3: fix VF reset on mailbox failure

Currently, during the VF reset, the VF will send a MBX to inform
PF to reset it and the disable command bit will be set whether
the MBX is successful. Generally, multiple reset attempts are made
after a failure. However, because the command is disabled, all
subsequent reset will all fail.

This patch disable the command only after the MBX message is
successfully.

Fixes: 2790c6464725 ("net/hns3: support device reset")
Cc: stable@dpdk.org
Signed-off-by: Chengchang Tang <tangchengchang@huawei.com>
Signed-off-by: Lijun Ou <oulijun@huawei.com>