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