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>
diff --git a/include/sound/soc.h b/include/sound/soc.h
index 82bd773..2ebf787 100644
--- a/include/sound/soc.h
+++ b/include/sound/soc.h
@@ -718,6 +718,7 @@
 	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;