ASoC: core: Add platform component mutex

Add mutex support for platform IO operations. e.g. can be used
for platform DAPM widget IO ops.

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

include/sound/soc.h

@@ -718,6 +718,7 @@ struct snd_soc_platform {
 	int id;
 	struct device *dev;
 	struct snd_soc_platform_driver *driver;
+	struct mutex mutex;
 
 	unsigned int suspended:1; /* platform is suspended */
 	unsigned int probed:1;

sound/soc/soc-core.c

@@ -3382,6 +3382,7 @@ int snd_soc_register_platform(struct device *dev,
 	platform->dapm.dev = dev;
 	platform->dapm.platform = platform;
 	platform->dapm.stream_event = platform_drv->stream_event;
+	mutex_init(&platform->mutex);
 
 	mutex_lock(&client_mutex);
 	list_add(&platform->list, &platform_list);