ASoC: utils: Add internal call to determine if DAI is dummy.

Provide a quick way to tell if a DAI is a dummy DAI or a regular DAI.
This is for internal DAPM usage only and is used to determine whether to
insert a DAI link connection into the DAPM graph.

Signed-off-by: Liam Girdwood <liam.r.girdwood@linux.intel.com>
Signed-off-by: Mark Brown <broonie@linaro.org>
diff --git a/sound/soc/soc-utils.c b/sound/soc/soc-utils.c
index 5e63365..d14bdb3 100644
--- a/sound/soc/soc-utils.c
+++ b/sound/soc/soc-utils.c
@@ -123,6 +123,13 @@
 	 },
 };
 
+int snd_soc_dai_is_dummy(struct snd_soc_dai *dai)
+{
+	if (dai->driver == &dummy_dai)
+		return 1;
+	return 0;
+}
+
 static int snd_soc_dummy_probe(struct platform_device *pdev)
 {
 	int ret;