ASoC: ak4671: Convert to direct regmap API usage

This helps us remove the ASoC level I/O functionality which is now just
a thin wrapper around regmap.
Signed-off-by: Mark Brown <broonie@linaro.org>

sound/soc/codecs/ak4671.h

@@ -105,8 +105,6 @@
 #define AK4671_DIGITAL_MIXING_CONTROL2		0x59
 #define AK4671_SAR_ADC_CONTROL			0x5a
 
-#define AK4671_CACHEREGNUM			(AK4671_SAR_ADC_CONTROL + 1)
-
 /* Bitfield Definitions */
 
 /* AK4671_AD_DA_POWER_MANAGEMENT (0x00) Fields */