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: I934c252283d1346f9c1f6cf786ce2f661f20a049

Signed-off-by: flar2 <asegaert@gmail.com>