- Split transmit queue into one for each type. Apparently there will
be a race when using a single active queue for all transmit types.
- Last argument of usb_pause_mtx() is ticks and not milliseconds.
- Remove unused watchdog.
- Remove some unused fields from the RSU softc structure.
- Workaround usbd_transfer_start() recursion from inside of completion
callback.

MFC after:	3 days