StreamSPI: use waitRequestByteTransfer() instead of raw raiseInterrupt()

Signed-off-by: Federico Vaga <federicov@linino.org>
StreamSPI: re-write state machine

Signed-off-by: Federico Vaga <federicov@linino.org>
StreamSPI: fix retrieve flags

Signed-off-by: Federico Vaga <federicov@linino.org>
StreamSPI: do not retrieve on empty frame

Signed-off-by: Federico Vaga <federicov@linino.org>
StreamSPI: add debug information

Signed-off-by: Federico Vaga <federicov@linino.org>