ASoC: Hold client_mutex while calling snd_soc_instantiate_cards()

As the comments of snd_soc_instantiate_cards() said,
snd_soc_instantiate_cards() must be called with client_mutex.

Signed-off-by: Axel Lin <axel.lin@gmail.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

sound/soc/soc-core.c

@@ -3072,7 +3072,9 @@ int snd_soc_register_dais(struct device *dev,
 		pr_debug("Registered DAI '%s'\n", dai->name);
 	}
 
+	mutex_lock(&client_mutex);
 	snd_soc_instantiate_cards();
+	mutex_unlock(&client_mutex);
 	return 0;
 
 err: