hwmon: update sysfs interface document - error handling

Here is a patch adding some text to the sysfs interface documentation on how
settings written to sysfs attributes should be handled, focussing mainly on
error handling. This version incorperates Jean's latest comments.

Signed-off-by: Hans de Goede <j.w.r.degoede@hhs.nl>
Acked-by: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Mark M. Hoffman <mhoffman@lightlink.com>