When SR-IOV is disabled (VF Enable is cleared), NumVFs is not very useful,
so this patch clears it out to prevent confusing lspci output like that
below.  We already clear NumVFs in sriov_disable(), and this does the same
when we disable SR-IOV as part of parsing the SR-IOV capability.

  $ lspci -vvv -s 13:00.0
  13:00.0 Ethernet controller: Intel Corporation 82599EB 10-Gigabit SFI/SFP+ Network Connection (rev 01)
      Capabilities: [160 v1] Single Root I/O Virtualization (SR-IOV)
          IOVCtl: Enable- Migration- Interrupt- MSE- ARIHierarchy+
          Initial VFs: 64, Total VFs: 64, Number of VFs: 64, ...

[bhelgaas: changelog]
Signed-off-by: Nethan.zhao <ethan.kernel@gmail.com>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>