Add qgraph nodes for virtio-balloon-pci and virtio-balloon-device.
Both nodes produce virtio-balloon, but virtio-balloon-pci receives
a pci-bus and uses virtio-pci QOSGraphObject and functions,
while virtio-balloon-device receives a virtio and implements
its own functions
Signed-off-by: Emanuele Giuseppe Esposito <e.emanuelegiuseppe@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>