ASoC: Constify snd_soc_dai_ops variables

The snd_soc_dai_ops variables are not modified after initialization in
these drivers, so make them const.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/codecs/max98357a.c

@@ -79,7 +79,7 @@ static struct snd_soc_codec_driver max98357a_codec_driver = {
 	.num_dapm_routes	= ARRAY_SIZE(max98357a_dapm_routes),
 };
 
-static struct snd_soc_dai_ops max98357a_dai_ops = {
+static const struct snd_soc_dai_ops max98357a_dai_ops = {
 	.trigger	= max98357a_daiops_trigger,
 };