pcm: iec958: implement HDMI HBR audio formatting

pcm: iec958: implement HDMI HBR audio formatting

High bitrate compressed audio data like DTS HD or MAT is usually
packed into 8-channel data. The HDMI specs state this has to be
formatted as a single IEC958 stream, compared to normal multi-
channel PCM data which has to be formatted as parallel IEC958 streams.

As this single-stream formatting mode may break existing setups that
expect non-PCM multichannel data to be formatted as parallel IEC958
streams it needs to be explicitly selected by setting the hdmi_mode
option to true.

The single-stream formatting implementation is prepared to cope with
arbitrary channel counts but only limited testing was done for channel
counts other than 8.

Signed-off-by: Matthias Reichl <hias@horus.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>