Add I2S-PCM slave mode for SCO

 * M7 needs us to configure I2SPCM for SCO and set the voice mode.

Change-Id: I98a9528af62f9c4fef075927f00a8aafdbeb4ee3
bluedroid: Remove ALSA check on sample rate setting

 * All QC devices using the CodeAurora drivers should be using a 48KHz
   samplerate for A2DP.

Change-Id: I8cec354c5a2dde0f85f19cfee2f75501f2a2d5a3