Bluetooth: A2DP sink interface for Audio Focus change and AVRCP 1.3

 - Add interface to report audio focus change from Bluetooth Apk
   to media task for A2DP Sink scenarios.
 - Add interface to request audiofocus from system/bt.
 - Add interfaces for AVRCP 1.3.

Change-Id: I687ea7be460b3ee3b082db9264621e2e24d04c0c
2 files changed