msm8226: add echo reference mixer control

Adding the mixer control for echo reference.
This change removes the hardcoding and adds mixer
control in the xml file.

Change-Id: I55a9cadaebb805d092098421bcb264a93b93faf1
Merge "msm8226: add echo reference mixer control"
Enable DSP-based AEC and NS for WebRTC

Change-Id: Ib001affd28a964c5b21758afb6d124f874c0dc49
Merge "Enable DSP-based AEC and NS for WebRTC"
msm8226: Move ECNS configuration flag

Move ECNS configuration flag to common makefile b2g_product.mk

Change-Id: I24775a00fd3890d002b3a5b7b0da40bb7ad49e8c
Merge "msm8226: Move ECNS configuration flag"