alsa_sound: Initial bring up of audio

Initial bring up of basic audio.

Change-Id: I70f527b7d2b5ae268d3e6a1534ca1faf14b6b272
alsa_sound: Enable MSM AudioPolicyManager

-Update AudioPolicyManagerALSA class as per changes
in AudioPolicyManagerBase class.
-Enable the derived AudioPolicyManager.

Change-Id: I2426268c5a3a1b12b03cef2fa75ee661ecc78599