metasound: add last missing modes (8kHz @ 6kbps per channel)

Signed-off-by: Anton Khirnov <anton@khirnov.net>
MSN Audio support

This is essentially a MS GSM decoder extension that supports more
sampling rates and lower bitrates.

Signed-off-by: Anton Khirnov <anton@khirnov.net>
mpeg12dec: Extract CC user data into frame side data

Signed-off-by: Anton Khirnov <anton@khirnov.net>