stereo call recording support

Patch that allows for call recording in
stereo (left channel: TX; right channel:
RX). Tested on Nexus 5 (MSM8974). Likely
works on other recent MSM chipsets as
well.

Change-Id: I132644ff26750c39c499321ec69e7c58d1aa456d
Merge remote-tracking branch 'upstream/cm-11.0' into clean-cm-11.0