This commit removes the ability to reserve a header in the data buffer of an
allocated URB. The header was required for a now defunct implementation of a
synchronous USB Host library API. Thus, headers are no longer required in
URB data buffers.
This commit adds the preliminary version of the USB Host Library. This commit contains:
- USBH (USB Host Driver)
- Hub Driver that only supports a single device and device enumeration
- USB Host Library (asychronous API)
- Test cases for USB Host Library asychronous API
The following changes were made to the existing HCD:
- Removed HCD_PIPE_STATE_INVALID. Pipes are no longer invalidated
- Changed pipe commands to halt, flush, and clear. Pipes need to be manually
halted, flush, and cleared.
- Halting and flushing a pipe will execute the pipe callback if it causes a
HCD_PIPE_EVENT_URB_DONE event
