Fixed processing of done ITDs and some debug stuff

* re-enable next_done_descriptor in ITD to fix it's finishing;
* add hard-code 1000 Hz generation to check endpoint data flow and
  assure that feeding is finaly working;
* delay interrupt on the last ITD increased from 0 to 1 to let the HCD
  finish descriptor utilizing and to read more correct status info.
Debugging and improving usb audio driver

* Some functionality like recording disabled;
* set the endpoint speed call added;
* packet size hard-coded to 48kHz case.