pci: Add interface names to hybrid PCI devices

pci: Add interface names to hybrid PCI devices

The following devices support both PCI Express and Conventional
PCI, by including special code to handle the QEMU_PCI_CAP_EXPRESS
flag and/or conditional pcie_endpoint_cap_init() calls:

* vfio-pci (is_express=1, but legacy PCI handled by
  vfio_populate_device())
* vmxnet3 (is_express=0, but PCIe handled by vmxnet3_realize())
* pvscsi (is_express=0, but PCIe handled by pvscsi_realize())
* virtio-pci (is_express=0, but PCIe handled by
  virtio_pci_dc_realize(), and additional legacy PCI code at
  virtio_pci_realize())
* base-xhci (is_express=1, but pcie_endpoint_cap_init() call
  is conditional on pci_bus_is_express(dev->bus)
  * Note that xhci does not clear QEMU_PCI_CAP_EXPRESS like the
    other hybrid devices

Cc: Dmitry Fleytman <dmitry@daynix.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Alex Williamson <alex.williamson@redhat.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Marcel Apfelbaum <marcel@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>