alsa_sound: Enable MSM AudioPolicyManager

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

Change-Id: I2426268c5a3a1b12b03cef2fa75ee661ecc78599
msm8660: update audio policy

based off http://review.cyanogenmod.org/#/c/52982/

Change-Id: I8fdd2cec421e7b1b715c899c8d10b7a00261a2d4