ASoC: rt5640: enable MCLK detection

There is a power saving mechanism in rt5640. It will turn off some
unused power when MCLK is not present. We call that "MCLK detection"
and it should be enabled by default.
Signed-off-by: Bard Liao <bardliao@realtek.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/codecs/rt5640.c

@@ -2407,6 +2407,9 @@ static int rt5640_i2c_probe(struct i2c_client *i2c,
 	if (ret != 0)
 		dev_warn(&i2c->dev, "Failed to apply regmap patch: %d\n", ret);
 
+	regmap_update_bits(rt5640->regmap, RT5640_DUMMY1,
+				RT5640_MCLK_DET, RT5640_MCLK_DET);
+
 	if (rt5640->pdata.in1_diff)
 		regmap_update_bits(rt5640->regmap, RT5640_IN1_IN2,
 					RT5640_IN_DF1, RT5640_IN_DF1);

sound/soc/codecs/rt5640.h

@@ -1970,6 +1970,8 @@
 #define RT5640_ZCD_HP_DIS			(0x0 << 15)
 #define RT5640_ZCD_HP_EN			(0x1 << 15)
 
+/* General Control 1 (0xfa) */
+#define RT5640_MCLK_DET				(0x1 << 11)
 
 /* Codec Private Register definition */
 /* 3D Speaker Control (0x63) */