hwmon: (adt7x10) Add device managed action for restoring config

To simplify the core driver remove function.

Signed-off-by: Cosmin Tanislav <cosmin.tanislav@analog.com>
Link: https://lore.kernel.org/r/20211221215841.2641417-3-demonsingur@gmail.com


[groeck: Adjust to use regmap; only register restore function if needed]
Tested-by: Cosmin Tanislav <cosmin.tanislav@analog.com>
Reviewed-by: Cosmin Tanislav <cosmin.tanislav@analog.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>