commit 30443408 upstream.

The third parameter for snd_pcm_format_set_silence needs the number
of samples instead of sample bytes.
Signed-off-by: Scott Jiang <scott.jiang.linux@gmail.com>
Signed-off-by: Mark Brown <broonie@linaro.org>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>