Notes by Ben:
This emulates a NEC/Renesas uPD720202 2-port (2 socket, 4-port register sets)
Root Hub xHCI Host Controller.
Many, many thanks to Renesas for their work and effort in helping my research.
I have tested in with my own tests and WinXP Home Edition SP3.
Use port1 and port2 to emulate a Super-speed device, and use port3 and port4
to emulate Low-, Full-, or High-speed devices.
NOTE: The Windows driver for this device uses a proprietary detection
mechanism and we don't have the permission to implement it. That's why it only
works fine with non-Windows guests.
