ASoC: max9768: Fix up review comments in max9768 driver

The Mute Switch should be called Playback Switch to match the volume
and the regmap core has been updated so we don't need to mark all the
registers as non-volatile.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Acked-by: Wolfram Sang <w.sang@pengutronix.de>

sound/soc/codecs/max9768.c

@@ -115,7 +115,7 @@ static const struct snd_kcontrol_new max9768_volume[] = {
 };
 
 static const struct snd_kcontrol_new max9768_mute[] = {
-	SOC_SINGLE_BOOL_EXT("Mute Switch", 0, max9768_get_gpio, max9768_set_gpio),
+	SOC_SINGLE_BOOL_EXT("Playback Switch", 0, max9768_get_gpio, max9768_set_gpio),
 };
 
 static int max9768_probe(struct snd_soc_codec *codec)
@@ -150,18 +150,12 @@ static struct snd_soc_codec_driver max9768_codec_driver = {
 	.num_controls = ARRAY_SIZE(max9768_volume),
 };
 
-static bool max9768_always_false(struct device *dev, unsigned int reg)
-{
-	return false;
-}
-
 static const struct regmap_config max9768_i2c_regmap_config = {
 	.reg_bits = 2,
 	.val_bits = 6,
 	.max_register = 3,
 	.reg_defaults = max9768_default_regs,
 	.num_reg_defaults = ARRAY_SIZE(max9768_default_regs),
-	.volatile_reg = max9768_always_false,
 	.cache_type = REGCACHE_RBTREE,
 };