hwmon: (max6639) Use regmap

Add regmap support & remove local caching.

Signed-off-by: Naresh Solanki <naresh.solanki@9elements.com>
Link: https://lore.kernel.org/r/20240503120020.3450972-1-naresh.solanki@9elements.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

Author: nsolanki22

drivers/hwmon/Kconfig

@@ -1233,6 +1233,7 @@ config SENSORS_MAX6621
 config SENSORS_MAX6639
 	tristate "Maxim MAX6639 sensor chip"
 	depends on I2C
+	select REGMAP_I2C
 	help
 	  If you say yes here you get support for the MAX6639
 	  sensor chips.