ASoC: nau8825: disable sinc filter for high THD of ADC

This bit will enable 4th order SINC filter.
=1, filter will enable;  but it consumes higher power.
=0, the sinc filter is disable, and it should always keep 0 value to
get high THD.

Therefor, disable the filter when codec initiation for better
performance when recording.
Signed-off-by: John Hsu <KCHSU0@nuvoton.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/codecs/nau8825.c

@@ -1846,7 +1846,8 @@ static void nau8825_init_regs(struct nau8825 *nau8825)
 	 * (audible hiss). Set it to something better.
 	 */
 	regmap_update_bits(regmap, NAU8825_REG_ADC_RATE,
-		NAU8825_ADC_SYNC_DOWN_MASK, NAU8825_ADC_SYNC_DOWN_64);
+		NAU8825_ADC_SYNC_DOWN_MASK | NAU8825_ADC_SINC4_EN,
+		NAU8825_ADC_SYNC_DOWN_64);
 	regmap_update_bits(regmap, NAU8825_REG_DAC_CTRL1,
 		NAU8825_DAC_OVERSAMPLE_MASK, NAU8825_DAC_OVERSAMPLE_64);
 	/* Disable DACR/L power */

sound/soc/codecs/nau8825.h

@@ -269,6 +269,8 @@
 #define NAU8825_BIQ_PATH_DAC   (1 << NAU8825_BIQ_PATH_SFT)
 
 /* ADC_RATE (0x2b) */
+#define NAU8825_ADC_SINC4_SFT		4
+#define NAU8825_ADC_SINC4_EN		(1 << NAU8825_ADC_SINC4_SFT)
 #define NAU8825_ADC_SYNC_DOWN_SFT	0
 #define NAU8825_ADC_SYNC_DOWN_MASK	0x3
 #define NAU8825_ADC_SYNC_DOWN_32	0