PCI: Set SR-IOV NumVFs to zero after enumeration

PCI: Set SR-IOV NumVFs to zero after enumeration

Orabug: 21547430

The enumeration path should leave NumVFs set to zero.  But after
4449f079722c ("PCI: Calculate maximum number of buses required for VFs"),
we call virtfn_max_buses() in the enumeration path, which changes NumVFs.
This NumVFs change is visible via lspci and sysfs until a driver enables
SR-IOV.

Set NumVFs to zero after virtfn_max_buses() computes the maximum number of
buses.

Fixes: 4449f079722c ("PCI: Calculate maximum number of buses required for VFs")
Based-on-patch-by: Ethan Zhao <ethan.zhao@oracle.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Ethan Zhao <ethan.zhao@oracle.com>