hwmon: (pwm-fan) Add support for using PWM FAN as a cooling device

The PWM FAN device can now be used as a thermal cooling device.

Signed-off-by: Lukasz Majewski <l.majewski@samsung.com>
Acked-by: Eduardo Valentin <edubezval@gmail.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>