ASoC: Constify ops and compr_ops fields of snd_soc_dai_link

The core does not modify these fields, so they can be made const. This allows
drivers to declare their op tables as const.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

include/sound/soc.h

@@ -904,8 +904,8 @@ struct snd_soc_dai_link {
 			struct snd_pcm_hw_params *params);
 
 	/* machine stream operations */
-	struct snd_soc_ops *ops;
-	struct snd_soc_compr_ops *compr_ops;
+	const struct snd_soc_ops *ops;
+	const struct snd_soc_compr_ops *compr_ops;
 };
 
 struct snd_soc_codec_conf {