misc: ti_fpc202: Support special-purpose GPIO lines with LED features

misc: ti_fpc202: Support special-purpose GPIO lines with 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.

Add support for the eight special-purpose GPIO lines to the existing FPC202
driver's GPIO support. Add support for registering led-class devices on
these GPIO lines.

Signed-off-by: Romain Gantois <romain.gantois@bootlin.com>
Link: https://patch.msgid.link/20260331-fpc202-leds-v3-3-74b173537d42@bootlin.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>