dt-bindings: hwmon: amc6821: add fan and PWM output

Add properties to describe the fan and the PWM controller output.

Link: https://www.ti.com/lit/gpn/amc6821


Signed-off-by: Francesco Dolcini <francesco.dolcini@toradex.com>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://lore.kernel.org/r/20250402102146.65406-2-francesco@dolcini.it


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