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: I3d8a99c21caf0205b7558148437a431e87bc0a85

Patchset: 2
http://review.cyanogenmod.org/#/c/65085/