hwmon: (pwm-fan) set usage_power on PWM state

PWM fans are controlled solely by the duty cycle of the PWM signal, they
do not care about the exact timing. Thus set usage_power to true to
allow less flexible hardware to work as a PWM source for fan control.

Signed-off-by: Lorenz Brun <lorenz@brun.one>
Link: https://lore.kernel.org/r/20230309011009.2109696-1-lorenz@brun.one


Signed-off-by: Guenter Roeck <linux@roeck-us.net>