hwmon: (adt7470) Add missing dependency on REGMAP_I2C

This driver requires REGMAP_I2C to be selected in order to get access to
regmap_config and devm_regmap_init_i2c. Add the missing dependency.

Fixes: ef67959c ("hwmon: (adt7470) Convert to use regmap")
Signed-off-by: Javier Carrasco <javier.carrasco.cruz@gmail.com>
Message-ID: <20241002-hwmon-select-regmap-v1-2-548d03268934@gmail.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>