2-way stereo call recording patch for msm8974

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.

source: https://code.google.com/p/2-way-call-recording/source/browse/patches/msm8974_stereo.patch
update defconfig for new features.