Add fan_max description.

Add fan limit alarm 'max_alarm' to the alarm section.
Signed-off-by: NChristian Engelmayer <christian.engelmayer@frequentis.com>
Acked-by: NHans de Goede <hdegoede@redhat.com>
Signed-off-by: NJean Delvare <khali@linux-fr.org>