gpio: aggregator: restore the set_config operation

Restore the set_config operation, as it was lost during the refactoring of
the gpio-aggregator driver while creating the gpio forwarder library.

Fixes: b31c68f ("gpio: aggregator: handle runtime registration of gpio_desc in gpiochip_fwd")
Reported-by: kernel test robot <oliver.sang@intel.com>
Closes: https://lore.kernel.org/oe-lkp/202509281206.a7334ae8-lkp@intel.com
Signed-off-by: Thomas Richard <thomas.richard@bootlin.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20250929-gpio-aggregator-fix-set-config-callback-v1-1-39046e1da609@bootlin.com
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

Author: thom24

drivers/gpio/gpio-aggregator.c

@@ -723,6 +723,7 @@ struct gpiochip_fwd *devm_gpiochip_fwd_alloc(struct device *dev,
 	chip->get_multiple = gpio_fwd_get_multiple_locked;
 	chip->set = gpio_fwd_set;
 	chip->set_multiple = gpio_fwd_set_multiple_locked;
+	chip->set_config = gpio_fwd_set_config;
 	chip->to_irq = gpio_fwd_to_irq;
 	chip->base = -1;
 	chip->ngpio = ngpios;