hwmon: (ads2828) Convert to use regmap

Simplify code and reduce code size by using regmap to access i2c registers.

Reviewed-and-Tested-by: Robert Rosengren <robert.rosengren@axis.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

drivers/hwmon/Kconfig

@@ -1389,6 +1389,7 @@ config SENSORS_ADS1015
 config SENSORS_ADS7828
 	tristate "Texas Instruments ADS7828 and compatibles"
 	depends on I2C
+	select REGMAP_I2C
 	help
 	  If you say yes here you get support for Texas Instruments ADS7828 and
 	  ADS7830 8-channel A/D converters. ADS7828 resolution is 12-bit, while