ASoC: dapm - FIXME -add locking to the DAPM power_widgets()

TODO: look into why _w is required.
FIXME: did oops in the past.

Signed-off-by: Liam Girdwood <lrg@ti.com>
diff --git a/include/sound/soc.h b/include/sound/soc.h
index 33db668..7eb53de 100644
--- a/include/sound/soc.h
+++ b/include/sound/soc.h
@@ -736,6 +736,7 @@
 
 	struct list_head list;
 	struct mutex mutex;
+	struct mutex dapm_mutex;
 
 	bool instantiated;