gpio: msc313: Convert to immutable irq_chip

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

This conversion follows the pattern of the gpio-ixp4xx
hierarchical GPIO interrupt driver.

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

drivers/gpio/gpio-msc313.c

···
 	return 0;
 }
 
+static void msc313_gpio_irq_mask(struct irq_data *d)
+{
+	struct gpio_chip *gc = irq_data_get_irq_chip_data(d);
+
+	irq_chip_mask_parent(d);
+	gpiochip_disable_irq(gc, d->hwirq);
+}
+
+static void msc313_gpio_irq_unmask(struct irq_data *d)
+{
+	struct gpio_chip *gc = irq_data_get_irq_chip_data(d);
+
+	gpiochip_enable_irq(gc, d->hwirq);
+	irq_chip_unmask_parent(d);
+}
+
 /*
  * The interrupt handling happens in the parent interrupt controller,
  * we don't do anything here.
  */
-static struct irq_chip msc313_gpio_irqchip = {
+static const struct irq_chip msc313_gpio_irqchip = {
 	.name = "GPIO",
 	.irq_eoi = irq_chip_eoi_parent,
-	.irq_mask = irq_chip_mask_parent,
-	.irq_unmask = irq_chip_unmask_parent,
+	.irq_mask = msc313_gpio_irq_mask,
+	.irq_unmask = msc313_gpio_irq_unmask,
 	.irq_set_type = irq_chip_set_type_parent,
 	.irq_set_affinity = irq_chip_set_affinity_parent,
+	.flags = IRQCHIP_IMMUTABLE,
+	GPIOCHIP_IRQ_RESOURCE_HELPERS,
 };
 
 /*
···
 	gpiochip->names = gpio->gpio_data->names;
 
 	gpioirqchip = &gpiochip->irq;
-	gpioirqchip->chip = &msc313_gpio_irqchip;
+	gpio_irq_chip_set_chip(gpioirqchip, &msc313_gpio_irqchip);
 	gpioirqchip->fwnode = of_node_to_fwnode(dev->of_node);
 	gpioirqchip->parent_domain = parent_domain;
 	gpioirqchip->child_to_parent_hwirq = msc313e_gpio_child_to_parent_hwirq;