gpio: idt3243x: Convert to immutable irq_chip

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

Cc: Marc Zyngier <[e-mail]>
Tested-by: Thomas Bogendoerfer <[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-idt3243x.c

···
 	writel(ctrl->mask_cache, ctrl->pic + IDT_PIC_IRQ_MASK);
 
 	raw_spin_unlock_irqrestore(&gc->bgpio_lock, flags);
+
+	gpiochip_disable_irq(gc, irqd_to_hwirq(d));
 }
 
 static void idt_gpio_unmask(struct irq_data *d)
···
 	struct idt_gpio_ctrl *ctrl = gpiochip_get_data(gc);
 	unsigned long flags;
 
+	gpiochip_enable_irq(gc, irqd_to_hwirq(d));
 	raw_spin_lock_irqsave(&gc->bgpio_lock, flags);
 
 	ctrl->mask_cache &= ~BIT(d->hwirq);
···
 	return 0;
 }
 
-static struct irq_chip idt_gpio_irqchip = {
+static const struct irq_chip idt_gpio_irqchip = {
 	.name = "IDTGPIO",
 	.irq_mask = idt_gpio_mask,
 	.irq_ack = idt_gpio_ack,
 	.irq_unmask = idt_gpio_unmask,
-	.irq_set_type = idt_gpio_irq_set_type
+	.irq_set_type = idt_gpio_irq_set_type,
+	.flags = IRQCHIP_IMMUTABLE,
+	GPIOCHIP_IRQ_RESOURCE_HELPERS,
 };
 
 static int idt_gpio_probe(struct platform_device *pdev)
···
 			return parent_irq;
 
 		girq = &ctrl->gc.irq;
-		girq->chip = &idt_gpio_irqchip;
+		gpio_irq_chip_set_chip(girq, &idt_gpio_irqchip);
 		girq->init_hw = idt_gpio_irq_init_hw;
 		girq->parent_handler = idt_gpio_dispatch;
 		girq->num_parents = 1;