hwmon: add fault attribute for voltage channels

Sometimes a voltage channel might have an hard failure (eg: a shorted
MOSFET). Hence, add a fault attribute to report such failures.

Signed-off-by: Nuno Sa <nuno.sa@analog.com>
Link: https://lore.kernel.org/r/20240129-b4-ltc4282-support-v4-2-fe75798164cc@analog.com


Signed-off-by: Guenter Roeck <linux@roeck-us.net>