audio: add missing QCOM_AUDIO_VARIANT check

Change-Id: I9e28b66e9680c2193245d32ef9555a14108ddb21
audio-caf: resurrect msm8660 audio

  * based on http://review.cyanogenmod.org/#/c/53023/ which was
    based on http://review.cyanogenmod.org/#/c/52982/

Change-Id: I7369d744282f384d6a9ed78f1b14efad7eb0d567
audio-caf: fix build when QCOM_USBAUDIO_ENABLED = false

Change-Id: I18ef8967d540c7104c465ddcc5ff19dbcbbdd2bd
legacy/msm8660: Enable support for LPA/Tunnel audio playback

 - based off http://review.cyanogenmod.org/#/c/53196

Change-Id: I12edbf103fe3a5a81451d2b4242bf77342b64ff9