This patch provides support for FastStream codec in bluetooth A2DP profile.
FastStream codec is bi-directional, which means that it supports both music
playback and microphone voice at the same time.

FastStream codec is just SBC codec with fixed parameters. For playback are
used following parameters: 48.0kHz or 44.1kHz, Blocks 16, Sub-bands 8,
Joint Stereo, Loudness, Bitpool = 29 (data rate = 212kbps, packet size =
(71+1)*3 <= DM5 = 220, with 3 SBC frames). SBC frame size is 71 bytes, but
FastStream is zero-padded to the even size (72). For microphone are used
following SBC parameters: 16kHz, Mono, Blocks 16, Sub-bands 8, Loudness,
Bitpool = 32 (data rate = 72kbps, packet size = 72*3 <= DM5 = 220, with
3 SBC frames).

So FastStream codec is equivalent to SBC in Low Quality settings. But the
main benefit of FastStream codec is support for microphone voice channel
for audio calls. Compared to bluetooth HSP profile (with CVSD codec), it
provides better audio quality for both playback and recording.