ASoC: ak4642: Implement suspend callback

Add the suspend callback to accompany the existing resume operation.
With the suspend/resume callbacks the regmap (regcache) state handling can
follow the recommended sequence.
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/codecs/ak4642.c

@@ -523,15 +523,23 @@ static struct snd_soc_dai_driver ak4642_dai = {
 	.symmetric_rates = 1,
 };
 
-static int ak4642_resume(struct snd_soc_codec *codec)
+static int ak4642_suspend(struct snd_soc_codec *codec)
 {
 	struct regmap *regmap = dev_get_regmap(codec->dev, NULL);
 
+	regcache_cache_only(regmap, true);
 	regcache_mark_dirty(regmap);
-	regcache_sync(regmap);
 	return 0;
 }
 
+static int ak4642_resume(struct snd_soc_codec *codec)
+{
+	struct regmap *regmap = dev_get_regmap(codec->dev, NULL);
+
+	regcache_cache_only(regmap, false);
+	regcache_sync(regmap);
+	return 0;
+}
 static int ak4642_probe(struct snd_soc_codec *codec)
 {
 	struct ak4642_priv *priv = snd_soc_codec_get_drvdata(codec);
@@ -544,6 +552,7 @@ static int ak4642_probe(struct snd_soc_codec *codec)
 
 static struct snd_soc_codec_driver soc_codec_dev_ak4642 = {
 	.probe			= ak4642_probe,
+	.suspend		= ak4642_suspend,
 	.resume			= ak4642_resume,
 	.set_bias_level		= ak4642_set_bias_level,
 	.controls		= ak4642_snd_controls,