[status report #3 & #4] USB device passthrough support on BHyVe

[Takuya ASADA]

[project summary]
The project goal is to support USB 1.1/2.0 device passthrough on BHyVe.

[weekly status]
* porting UHCI emulator
- Initial implementation of IO space read/write handling
- Interrupt support using legacy intr(non msi)
- Implemented timer helper functions
- Better debug message
- Fixes of controller initialization

As a result, now guest kernel able to detect uhci0 (with an error message,
though.)
Here's a guest dmesg output:

uhci0: <Intel 82801I (ICH9) USB controller> port 0x2040-0x205f irq 9 at
device 2.0 on pci0
uhci0: USB revision is unknown. Assuming v1.1.
uhci0: LegSup = 0x0000
usbus0: controller did not stop
usbus0 on uhci0
usbus0: 12Mbps Full Speed USB v1.1
ugen0.1: <Intel> at usbus0
uhub0: <Intel UHCI root HUB, class 9/0, rev 1.00/1.00, addr 1> on usbus0
Root mount waiting for: usbus0
uhub0: 2 ports with 2 removable, self powered