ASoC: Fix check for symmetric rate enforcement

The ASoC core tries to not enforce symmetric rates when
two streams open simultaneously. It does so by checking
rtd->rate being zero. This works exactly once after booting
because it is not set to zero again when the streams close.
Fix this by setting rtd->rate when no active stream is left.

[This leads to lots of warnings about not enforcing the symmetry in some
situations as there's a race in the userspace API where we know we've
got two applications but don't know what rates they want to set.
-- broonie ]
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

sound/soc/soc-pcm.c

@@ -290,6 +290,9 @@ static int soc_pcm_close(struct snd_pcm_substream *substream)
 	codec_dai->active--;
 	codec->active--;
 
+	if (!cpu_dai->active && !codec_dai->active)
+		rtd->rate = 0;
+
 	/* Muting the DAC suppresses artifacts caused during digital
 	 * shutdown, for example from stopping clocks.
 	 */