hwmon: (f71882fg) Add missing pwm3 attr for f71862fg

For some reason the fan_attr array for the f71862fg was missing the attr for
the 3th pwm output. This patch fixes this.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Jean Delvare <khali@linux-fr.org>