ASoC: Add kerneldoc comments for snd_soc_find_dai

snd_soc_find_dai() has been exported and so add the kerneldoc comments
for it.

Signed-off-by: Mengdong Lin <mengdong.lin@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/soc-core.c

@@ -930,6 +930,17 @@ static struct snd_soc_component *soc_find_component(
 	return NULL;
 }
 
+/**
+ * snd_soc_find_dai - Find a registered DAI
+ *
+ * @dlc: name of the DAI and optional component info to match
+ *
+ * This function will search all regsitered components and their DAIs to
+ * find the DAI of the same name. The component's of_node and name
+ * should also match if being specified.
+ *
+ * Return: pointer of DAI, or NULL if not found.
+ */
 struct snd_soc_dai *snd_soc_find_dai(
 	const struct snd_soc_dai_link_component *dlc)
 {