ASoC: renesas: rsnd: allow to use ADG as standalone

Audio clock generator (= ADG) can be used standalone (without DAI),
but current driver indicates error if it doesn't have DAI on DT.
It is not error, allow to use ADG as standalone.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Link: https://patch.msgid.link/87v7r22x0a.wl-kuninori.morimoto.gx@renesas.com
Signed-off-by: Mark Brown <broonie@kernel.org>

Author: morimoto

sound/soc/renesas/rcar/core.c

@@ -1482,8 +1482,13 @@ static int rsnd_dai_probe(struct rsnd_priv *priv)
 	int dai_i;
 
 	nr = rsnd_dai_of_node(priv, &is_graph);
+
+	/*
+	 * There is a case that it is used only for ADG (Sound Clock).
+	 * No DAI is not error
+	 */
 	if (!nr)
-		return -EINVAL;
+		return 0;
 
 	rdrv = devm_kcalloc(dev, nr, sizeof(*rdrv), GFP_KERNEL);
 	rdai = devm_kcalloc(dev, nr, sizeof(*rdai), GFP_KERNEL);