gpio: cadence: Convert to immutable irq_chip

Convert the driver to immutable irq-chip with a bit of
intuition.

Cc: Marc Zyngier <[e-mail]>
Acked-by: Marc Zyngier <[e-mail]>
Signed-off-by: Linus Walleij <[e-mail]>
Signed-off-by: Bartosz Golaszewski <[e-mail]>

drivers/gpio/gpio-cadence.c

···
 	struct cdns_gpio_chip *cgpio = gpiochip_get_data(chip);
 
 	iowrite32(BIT(d->hwirq), cgpio->regs + CDNS_GPIO_IRQ_DIS);
+	gpiochip_disable_irq(chip, irqd_to_hwirq(d));
 }
 
 static void cdns_gpio_irq_unmask(struct irq_data *d)
···
 	struct gpio_chip *chip = irq_data_get_irq_chip_data(d);
 	struct cdns_gpio_chip *cgpio = gpiochip_get_data(chip);
 
+	gpiochip_enable_irq(chip, irqd_to_hwirq(d));
 	iowrite32(BIT(d->hwirq), cgpio->regs + CDNS_GPIO_IRQ_EN);
 }
 
···
 	chained_irq_exit(irqchip, desc);
 }
 
-static struct irq_chip cdns_gpio_irqchip = {
+static const struct irq_chip cdns_gpio_irqchip = {
 	.name		= "cdns-gpio",
 	.irq_mask	= cdns_gpio_irq_mask,
 	.irq_unmask	= cdns_gpio_irq_unmask,
-	.irq_set_type	= cdns_gpio_irq_set_type
+	.irq_set_type	= cdns_gpio_irq_set_type,
+	.flags		= IRQCHIP_IMMUTABLE,
+	GPIOCHIP_IRQ_RESOURCE_HELPERS,
 };
 
 static int cdns_gpio_probe(struct platform_device *pdev)
···
 		struct gpio_irq_chip *girq;
 
 		girq = &cgpio->gc.irq;
-		girq->chip = &cdns_gpio_irqchip;
+		gpio_irq_chip_set_chip(girq, &cdns_gpio_irqchip);
 		girq->parent_handler = cdns_gpio_irq_handler;
 		girq->num_parents = 1;
 		girq->parents = devm_kcalloc(&pdev->dev, 1,