av: Additional ifdefs for QCOM DirectTrack

 * Tunnel and LPA mode on legacy QC devices requires the DirectTrack
   code path, which going forward has been deprecated.
 * In order to properly support QC features on 8974, this needs broken
   out in order to not cause problems on new devices.
 * With this patch, QCOM_HARDWARE will enable features common to all
   QC platforms (including legacy), and legacy support will
   automatically be enabled based on the use of driver variant and
   value of BOARD_USES_LEGACY_ALSA_AUDIO.

Change-Id: I1da503309963734fd6603472fb87dd9c95c7b7b5