dt-bindings: hwmon: adt7475: Allow and recommend #pwm-cells = <3>

To make this binding match what is usally used for PWMs, deprecate 4
cells and allow 3 instead.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@baylibre.com>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://lore.kernel.org/r/77895aec937b6217f513d3b12e7945f1707fd906.1750361514.git.u.kleine-koenig@baylibre.com


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