hwmon: (axi-fan-control) Support temperature vs pwm points

hwmon: (axi-fan-control) Support temperature vs pwm points

The HW has some predefined points where it will associate a PWM value.
However some users might want to better set these points to their
usecases. This patch exposes these points as pwm auto_points:

 * pwm1_auto_point1_temp_hyst: temperature threshold below which PWM should
   be 0%;
 * pwm1_auto_point1_temp: temperature threshold above which PWM should be
   25%;
 * pwm1_auto_point2_temp_hyst: temperature threshold below which PWM should
   be 25%;
 * pwm1_auto_point2_temp: temperature threshold above which PWM should be
   50%;
 * pwm1_auto_point3_temp_hyst: temperature threshold below which PWM should
   be 50%;
 * pwm1_auto_point3_temp: temperature threshold above which PWM should be
   75%;
 * pwm1_auto_point4_temp_hyst: temperature threshold below which PWM should
   be 75%;
 * pwm1_auto_point4_temp: temperature threshold above which PWM should be
   100%;

Signed-off-by: Nuno Sá <nuno.sa@analog.com>
Link: https://lore.kernel.org/r/20210811114853.159298-4-nuno.sa@analog.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>