net: hns3: handle empty unknown interrupt for VF

Since some interrupt states may be cleared by hardware, the driver
may receive an empty interrupt. Currently, the VF driver directly
disables the vector0 interrupt in this case. As a result, the VF
is unavailable. Therefore, the vector0 interrupt should be enabled
in this case.

Fixes: b90fcc5b

 ("net: hns3: add reset handling for VF when doing Core/Global/IMP reset")
Signed-off-by: Yufeng Mo <moyufeng@huawei.com>
Signed-off-by: Guangbin Huang <huangguangbin2@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>