ASoC: soc-core: remove null_snd_soc_ops

All rtd->dai_link callback functions are controlled by soc_rtd_xxxx(),
and checking rtd->dai_link->ops.
We don't need to have null_snd_soc_ops anymore.
This patch removes it.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Link: https://lore.kernel.org/r/87zhegl3oz.wl-kuninori.morimoto.gx@renesas.com
Reviewed-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/soc-core.c

@@ -342,8 +342,6 @@ struct snd_soc_component *snd_soc_lookup_component(struct device *dev,
 }
 EXPORT_SYMBOL_GPL(snd_soc_lookup_component);
 
-static const struct snd_soc_ops null_snd_soc_ops;
-
 struct snd_soc_pcm_runtime
 *snd_soc_get_pcm_runtime(struct snd_soc_card *card,
 			 struct snd_soc_dai_link *dai_link)
@@ -488,8 +486,6 @@ static struct snd_soc_pcm_runtime *soc_new_pcm_runtime(
 	 */
 	rtd->card = card;
 	rtd->dai_link = dai_link;
-	if (!rtd->dai_link->ops)
-		rtd->dai_link->ops = &null_snd_soc_ops;
 
 	/* see for_each_card_rtds */
 	list_add_tail(&rtd->list, &card->rtd_list);