ASoC: core: Return -ENOTSUPP instead of -EINVAL if mute is not supported

This helps us ignore errors in callers if the operation failed due to not
being available as opposed to an error.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Acked-by: Liam Girdwood <lrg@ti.com>

sound/soc/soc-core.c

@@ -3031,7 +3031,7 @@ int snd_soc_dai_digital_mute(struct snd_soc_dai *dai, int mute)
 	if (dai->driver && dai->driver->ops->digital_mute)
 		return dai->driver->ops->digital_mute(dai, mute);
 	else
-		return -EINVAL;
+		return -ENOTSUPP;
 }
 EXPORT_SYMBOL_GPL(snd_soc_dai_digital_mute);