PCI: Never treat a VF as a multifunction device

Per the SR-IOV spec rev 1.1:

  3.4.1.9 Header Type (Offset 0Eh)

  "... For VFs, this register must be RO Zero."

Unfortunately some devices get this wrong, ex. Emulex OneConnect 10Gb NIC.
When they do it makes us handle ACS testing and therefore IOMMU groups as
if they were actual multifunction devices and require ACS capabilities to
make sure there's no peer-to-peer between functions.  VFs are never
traditional multifunction devices, so simply clear this bit before we get
any further into setup.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=68431


Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>