by Nick Hibma):
use NULL not 0
declare all local definitions static
rename s/usbd_request/usbd_xfer/ s/reqh/xfer/
rename s/r/err/
use implicit test for no err
KNF
the device driver instead of happening automagically in the HC driver.
This affects both the HC-USBD interface as well as the USBD-device
interface.
This change will allow DMA buffers to be reused e.g. in isochronous
traffic.
Add isochronous support to the UHCI driver (not for OHCI yet).
