ASoC: dapm: Add helpers to lock/unlock DAPM mutex

Acquiring the DAPM mutex is necessary before using several DAPM
functions and dereference is quite ugly. This patch provides a helper
function to simplify this.

Signed-off-by: Charles Keepax <ckeepax@opensource.wolfsonmicro.com>
Signed-off-by: Mark Brown <broonie@linaro.org>
diff --git a/include/sound/soc.h b/include/sound/soc.h
index 9a00147..1e12b66 100644
--- a/include/sound/soc.h
+++ b/include/sound/soc.h
@@ -1188,4 +1188,15 @@
 
 extern const struct dev_pm_ops snd_soc_pm_ops;
 
+/* Helper functions */
+static inline void snd_soc_dapm_mutex_lock(struct snd_soc_dapm_context *dapm)
+{
+	mutex_lock(&dapm->card->dapm_mutex);
+}
+
+static inline void snd_soc_dapm_mutex_unlock(struct snd_soc_dapm_context *dapm)
+{
+	mutex_unlock(&dapm->card->dapm_mutex);
+}
+
 #endif