hwmon: (gpio-fan) Fix "#cooling-cells" property name in bindings

It should be "#cooling-cells" instead of "cooling-cells". Fix it.
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
[groeck: Updated subject]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

Documentation/devicetree/bindings/hwmon/gpio-fan.txt

@@ -11,7 +11,7 @@ Optional properties:
   must have the RPM values in ascending order.
 - alarm-gpios: This pin going active indicates something is wrong with
   the fan, and a udev event will be fired.
-- cooling-cells: If used as a cooling device, must be <2>
+- #cooling-cells: If used as a cooling device, must be <2>
   Also see: Documentation/devicetree/bindings/thermal/thermal.txt
   min and max states are derived from the speed-map of the fan.