hal: Add suport for dedicated VoIP devices

 * Some devices out there have dedicated paths for VoIP, add support
   for these by setting the system property.

Change-Id: I59cd97e78427f811559081a04151c9a2eccf452f
msm7x30: Sync audio_policy with alsa_sound

Change-Id: I8be0110f566c8f91d6a736471eaf614184cd0faa