SS_r4: Bluetooth: request audio focus on incoming call

When the a2dp stream is suspended for an incoming call, request audio
focus from the audio manager so that any playing media will pause/duck
as needed.

Change-Id: I308b697ad998b7167703ebc89c6285034ac1ebf9
Signed-off-by: Roman Birg <roman@cyngn.com>

DS_r4: Revert "Compilation Fix"

This reverts commit 6773aa72bcd0ebbc2a3005fb382b9bb64e5be180.