net: hns3: Add support of .sriov_configure in HNS3 driver

As HNS3 driver will enable SRIOV default and enable all VFs the
HW support, if PF and VF driver compiled to kernel, VF driver
will work on host default, it is not right.

This patch adds support for hns3_driver.sriov_configure to support
user configs the VF_num, and do not enable sriov default.

Signed-off-by: Peng Li <lipeng321@huawei.com>
Suggested-by: Zhou Wang <wangzhou1@hisilicon.com>
Signed-off-by: Salil Mehta <salil.mehta@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>