audio msm8974: new path for speaker phone with AEC

Added new path for voice/video chat mic when AEC is on
in speakerphone mode to allow different gain settings from
speakerphone in telephony.

Bug: 13279002.
Change-Id: If8f76c243f2bf8b5defae35ecf871510cc6fe41d
Merge tag 'android-4.4.3_r1' into kk-4.4

Android 4.4.3 release 1