ASoC: rsnd: ssi: add rsnd_ssi_of_node()

This patch adds rsnd_ssi_of_node() to get SSI subnode from DT.
This is prepare for new DT bindings for 1st DMAC
Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/sh/rcar/ssi.c

@@ -83,6 +83,8 @@ struct rsnd_ssi {
 #define rsnd_ssi_clk_from_parent(ssi) ((ssi)->parent)
 #define rsnd_ssi_mode_flags(p) ((p)->info->flags)
 #define rsnd_ssi_dai_id(ssi) ((ssi)->info->dai_id)
+#define rsnd_ssi_of_node(priv) \
+	of_get_child_by_name(rsnd_priv_to_dev(priv)->of_node, "rcar_sound,ssi")
 
 int rsnd_ssi_use_busif(struct rsnd_mod *mod)
 {
@@ -633,7 +635,7 @@ static void rsnd_of_parse_ssi(struct platform_device *pdev,
 	if (!of_data)
 		return;
 
-	node = of_get_child_by_name(dev->of_node, "rcar_sound,ssi");
+	node = rsnd_ssi_of_node(priv);
 	if (!node)
 		return;