PCI: Do not attempt to set ExtTag for VFs

PCI: Do not attempt to set ExtTag for VFs

The bit for enabling extended tags is Reserved and Preserved (RsvdP) for
VFs, according to PCIe r7.0 section 7.5.3.4 table 7.21.  Hence, bail out
early from pci_configure_extended_tags() if the device is a VF.

Otherwise, we may see incorrect log messages such as:

  kernel: pci 0000:af:00.2: enabling Extended Tags

(af:00.2 is a VF)

Fixes: 60db3a4d8cc9 ("PCI: Enable PCIe Extended Tags if supported")
Signed-off-by: Håkon Bugge <haakon.bugge@oracle.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Zhu Yanjun <yanjun.zhu@linux.dev>
Link: https://patch.msgid.link/20251112095442.1913258-1-haakon.bugge@oracle.com