vfio/migration: Modify the vf id acquisition method

driver inclusion
category:feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I6DRLU


CVE: NA

When using the old PCI_FUNC method to obtain the vf id, if the number
of vf big than 8, the obtained id number will be wrong, and the new
method needs to be used to correct it.

Signed-off-by: Longfang Liu <liulongfang@huawei.com>
Signed-off-by: JiangShui Yang <yangjiangshui@h-partners.com>