When playing multichannel data, the rear channels can get distorted if
the last sample of the last played stereo stream was not zero.  To avoid
this, add a hack to play a few silence samples after the stream is
stopped.
Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Jaroslav Kysela <perex@suse.cz>