Here we assume that if qemu supports generic PCI host controller,
it is a part of virt machine and can be used for adding PCI devices.

In qemu this is actually a PCIe bus, so we also declare multibus
capability so that 0'th bus is specified to qemu correctly as 'pcie.0'
Signed-off-by: NPavel Fedin <p.fedin@samsung.com>
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>