ASoC: soc-core: add comment for rtd freeing

We don't need to mind freeing for rtd,
because it was created from devm_kzalloc(dev, xxx) which is rtd->dev.

This means, if rtd->dev was freed, rtd will be also freed
automatically.

	soc_new_pcm_runtime(...)
	{
		...
		rtd = devm_kzalloc(dev, ...);
		rtd->dev = dev;
		...
	}

This explanation was missing at soc_free_pcm_runtime() comment.
This patch indicates it.
Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Link: https://lore.kernel.org/r/87sg4dxldn.wl-kuninori.morimoto.gx@renesas.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/soc-core.c

@@ -413,6 +413,14 @@ static void soc_free_pcm_runtime(struct snd_soc_pcm_runtime *rtd)
 	 * it is alloced *before* rtd.
 	 * see
 	 *	soc_new_pcm_runtime()
+	 *
+	 * We don't need to mind freeing for rtd,
+	 * because it was created from dev (= rtd->dev)
+	 * see
+	 *	soc_new_pcm_runtime()
+	 *
+	 *		rtd = devm_kzalloc(dev, ...);
+	 *		rtd->dev = dev
 	 */
 	device_unregister(rtd->dev);
 }