ASoC: dmic: declare trigger function as static

No reason why this is global, fix warnings with W=1
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/codecs/dmic.c

@@ -44,8 +44,8 @@ struct dmic {
 	int modeswitch_delay;
 };
 
-int dmic_daiops_trigger(struct snd_pcm_substream *substream,
-		int cmd, struct snd_soc_dai *dai)
+static int dmic_daiops_trigger(struct snd_pcm_substream *substream,
+			       int cmd, struct snd_soc_dai *dai)
 {
 	struct snd_soc_component *component = dai->component;
 	struct dmic *dmic = snd_soc_component_get_drvdata(component);