Remove unnecessary parameter for stt_start_file function

Remove unnecessary parameter for stt_start_file function

The audio format types are not changable in current STT engine.
Therefore sample rate, channel and audio type are not necessary to transmit the pcm data to cloud.
The application should send pcm data, which consits of 1 channel, 16000 sample rate and signed 16 bit pcm data.

Change-Id: I4f9ad034419bf088d6de9d2a1b4a54adfc6e718a