hwmon: Define a standard interface for chassis intrusion detection

Define a standard interface for the chassis intrusion detection feature
some hardware monitoring chips have. Some drivers have custom sysfs
entries for it, but a standard interface would allow integration with
user-space (namely libsensors.)

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Acked-by: Hans de Goede <j.w.r.degoede@hhs.nl>
Acked-by: Matt Roberds <mattroberds@cox.net>