dt-bindings: misc: Describe FPC202 LED features

dt-bindings: misc: Describe FPC202 LED features

The FPC202 dual port controller has 20 regular GPIO lines and 8 special
GPIO lines with LED features. Each one of these "LED GPIOs" can output PWM
and blink signals.

Describe these special-purpose GPIO lines.

Acked-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Romain Gantois <romain.gantois@bootlin.com>
Link: https://patch.msgid.link/20260331-fpc202-leds-v3-2-74b173537d42@bootlin.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>