hwmon: (max6620) Update broken Datasheet URL in driver documentation

The URL for the MAX6620 datasheet has changed. Update it to reflect the
current location.

Signed-off-by: Okan Akyuz <okanakyuz@okanakyuz.com>
Link: https://lore.kernel.org/r/20240216075212.69118-1-okanakyuz@okanakyuz.com


[groeck: Updated subject and patch description]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>