Add qgraph nodes for virtio-blk-pci and virtio-blk-device.
Both nodes produce virtio-blk, but virtio-blk-pci receives
a pci-bus and uses virtio-pci QOSGraphObject and functions,
while virtio-blk-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>
