hwmon: Document temp[1-*]_min_hyst sysfs attribute

The temp[1-*]_min_hyst sysfs attribute is already implemented by 3
hwmon drivers (adt7x10, lm77 and lm92) but was missing from the
standard interface.

Also add temp[1-*]_lcrit_hyst for consistency, even though no driver
implement that one for the time being.

Signed-off-by: Jean Delvare <jdelvare@suse.de>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>