gpio: bcm-kona: make irq_chip immutable

The gpiolib is moving to make irq_chip immutable, otherwise
there is warning: "not an immutable chip, please consider fixing it!"

The bcm_gpio_irq_chip already has irq hooks configured correctly,
bcm_kona_gpio_irq_mask/bcm_kona_gpio_irq_unmask calls gpiochip_disable_irq/
gpiochip_enable_irq, and bcm_kona_gpio_irq_reqres/irq_release_resources
calls gpiochip_reqres_irq/gpiochip_relres_irq.

So just need to  flag it as IRQCHIP_IMMUTABLE.

Signed-off-by: Peng Fan <peng.fan@nxp.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20250509-gpio-v1-1-639377c98288@nxp.com
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

Author: MrVan

drivers/gpio/gpio-bcm-kona.c

@@ -516,6 +516,7 @@ static struct irq_chip bcm_gpio_irq_chip = {
 	.irq_set_type = bcm_kona_gpio_irq_set_type,
 	.irq_request_resources = bcm_kona_gpio_irq_reqres,
 	.irq_release_resources = bcm_kona_gpio_irq_relres,
+	.flags = IRQCHIP_IMMUTABLE,
 };
 
 static struct of_device_id const bcm_kona_gpio_of_match[] = {