ASoC: Add a sanity check before using dai driver name

The dai driver's name is allowed to be NULL. So add a sanity check for
that.
Signed-off-by: Jeffy Chen <jeffy.chen@rock-chips.com>
Reported-by: Donglin Peng <dolinux.peng@gmail.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/soc-core.c

@@ -1029,7 +1029,8 @@ struct snd_soc_dai *snd_soc_find_dai(
 			continue;
 		list_for_each_entry(dai, &component->dai_list, list) {
 			if (dlc->dai_name && strcmp(dai->name, dlc->dai_name)
-			    && strcmp(dai->driver->name, dlc->dai_name))
+			    && (!dai->driver->name
+				|| strcmp(dai->driver->name, dlc->dai_name)))
 				continue;
 
 			return dai;