ASoC: audio-graph-card2: add comment for format property

We don't need to have "format" property on DT any more if
CPU/Codec driver has .auto_selectable_formats settings
on snd_soc_dai_ops. The sample dtsi doesn't have it.
To avoid user confusion, this patch indicates it on comment.
Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Link: https://lore.kernel.org/r/87edjuzk2p.wl-kuninori.morimoto.gx@renesas.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/generic/audio-graph-card2-custom-sample.dtsi

@@ -34,6 +34,13 @@
  *		...
  *	};
  *
+ *
+ * Below sample doesn't use "format" property,
+ * because test-component driver (test-cpu/test-codec) is supporting
+ * snd_soc_dai_ops :: .auto_selectable_formats.
+ * see
+ *	snd_soc_runtime_get_dai_fmt()
+ *	linux/sound/soc/generic/test-component.c :: test_dai_formats
  */
 / {
 	/*

sound/soc/generic/audio-graph-card2.c

@@ -47,6 +47,18 @@
  see
 	graph_parse_daifmt().
 
+ "format" property is no longer needed on DT if both CPU/Codec drivers are
+ supporting snd_soc_dai_ops :: .auto_selectable_formats.
+ see
+	snd_soc_runtime_get_dai_fmt()
+
+	sample driver
+		linux/sound/soc/sh/rcar/core.c
+		linux/sound/soc/codecs/ak4613.c
+		linux/sound/soc/codecs/pcm3168a.c
+		linux/sound/soc/soc-utils.c
+		linux/sound/soc/generic/test-component.c
+
  ************************************
 	Normal Audio-Graph
  ************************************