bluetooth: Add avrcp_absolute_volume module flag for disablement

Not all peers might work fine with Absolute Volume, provide the user
with an option to disable it without impairing other AVRCP-related
commands like media status and playback controls.

Part-of: <pulseaudio/pulseaudio!239>
2 jobs for a2dp-avrcp-absolute-volume in 2 minutes and 31 seconds (queued for 3 seconds)