audioflinger: Use channel count for buffer size calculation

- For VOIP(hangout) usecase, when the ringtone is played,
  application sets flag as VOIP and the channel as stereo.
  But , on the server (audioflinger) side , the channel
  was always considered as MONO. This was leading to a
  corruption of the Cblk.
- Added changes to consider channel count in allocating the
  buffer size.

CRs-Fixed: 523984 522525

Change-Id: I160d7cf7855161efa201a86846aec67cb24d35dd
Merge "audioflinger: Use channel count for buffer size calculation" into jb4.3