hwmon: (max6697) add missing 'select REGMAP_I2C' to Kconfig

hwmon: (max6697) add missing 'select REGMAP_I2C' to Kconfig

The Kconfig entry for the MAX6697 sensor doesn't contain a
`select REGMAP_I2C` parameter, causing build failures if regmap
isn't selected previously during the build process.

Fixes: 3a2a8cc3fe24 ("hwmon: (max6697) Convert to use regmap")
Cc: stable@vger.kernel.org
Signed-off-by: Joshua Crofts <joshua.crofts1@gmail.com>
Link: https://lore.kernel.org/r/20260629-add-kconfig-deps-v1-3-8104df929b1a@gmail.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>