hdl: fixup DAC SPI routing condition
libbladeRF: Added missing CALL_CONV's and corrected Doxygen annotations
libbladeRF: Removed duplicate code from sync_deinit()

The switch() statement here was a vestige from when there were
different condition variables (buf_produced/buf_consumed) that would
need to be passed to sync_worker_deinit().
libbladeRF: Set stream error code on unexpected libusb transfer error
libbladeRF: Propagate stream failure back to sync_rx/tx caller

The error codes from stream failures now work their way back to the
bladerf_sync_rx/tx caller.  Previously, such a failure would either
cause these calls to timeout (when a nonzero timeout_ms parameter was
provided), or (incorrectly) lock up waiting on a buffer while the stream
worker was idle.
libbladeRF: Reduced Error/Warning log level to Debug for lower-level errors

These messages don't mean much to folks not intimately involved with the
underlying libbladeRF code base, and the return codes already indicate
that a failure occurred.

Therefore, the Debug level is more appropriate here.
libbladeRF: [WIP] Renamed and moved backend function table items
libbladeRF: [WIP] Started copying over USB fns
Added a few more usb fns
libbladeRF: [WIP] Working through compilation errors
[WIP] Additional build fixes
libbladeRF: [WIP] Fixed structure renaming build breaker
libbladeRF: [WIP] Reorganized backend-related code, moved to backend/
libbladeRF: [WIP] Stubbed out new libusb backend
libbladeRF: [WIP] Added a few libusb backend functions
libbladeRF: [WIP] Rebased against current master, added new backend fns
libbladeRF: [WIP] Added probe to new backend
libbladeRF: [WIP] Refactored open code

Moving logic out of (libusb) backend and up into top-level, where
possible, and the USB middle layer when possible.
libbladeRF: [WIP] Added remaining libusb backend functions
libbladeRF: [WIP] Debugging device open/close