This patch enables MSI-X for virtfs-9p-pci.  It also adds a
compat property to pc-0.13 which turns it of there to stay
compatible to 0.13-stable.
Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>