Introduce PCI_VENDOR/PCI_SUBVENDOR/PCI_SUBDEVICE defines to replace the
constants scattered in the kernel already used to detect QEMU.

They are defined in the QEMU codebase per docs/specs/pci-ids.txt.
Signed-off-by: NRobin H. Johnson <robbat2@gentoo.org>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>
Reviewed-by: NTakashi Iwai <tiwai@suse.de>
Reviewed-by: NGerd Hoffmann <kraxel@redhat.com>
Acked-by: NMichael S. Tsirkin <mst@redhat.com>
Acked-by: NDaniel Vetter <daniel.vetter@ffwll.ch>