gpio: 104-idio-16: Make irq_chip immutable

Kernel warns about mutable irq_chips:

    "not an immutable chip, please consider fixing!"

Make the struct irq_chip const, flag it as IRQCHIP_IMMUTABLE, add the
new helper functions, and call the appropriate gpiolib functions.
Signed-off-by: William Breathitt Gray <william.gray@linaro.org>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>

drivers/gpio/gpio-104-idio-16.c

@@ -174,10 +174,11 @@ static void idio_16_irq_mask(struct irq_data *data)
 {
 	struct gpio_chip *chip = irq_data_get_irq_chip_data(data);
 	struct idio_16_gpio *const idio16gpio = gpiochip_get_data(chip);
-	const unsigned long mask = BIT(irqd_to_hwirq(data));
+	const unsigned long offset = irqd_to_hwirq(data);
 	unsigned long flags;
 
-	idio16gpio->irq_mask &= ~mask;
+	idio16gpio->irq_mask &= ~BIT(offset);
+	gpiochip_disable_irq(chip, offset);
 
 	if (!idio16gpio->irq_mask) {
 		raw_spin_lock_irqsave(&idio16gpio->lock, flags);
@@ -192,11 +193,12 @@ static void idio_16_irq_unmask(struct irq_data *data)
 {
 	struct gpio_chip *chip = irq_data_get_irq_chip_data(data);
 	struct idio_16_gpio *const idio16gpio = gpiochip_get_data(chip);
-	const unsigned long mask = BIT(irqd_to_hwirq(data));
+	const unsigned long offset = irqd_to_hwirq(data);
 	const unsigned long prev_irq_mask = idio16gpio->irq_mask;
 	unsigned long flags;
 
-	idio16gpio->irq_mask |= mask;
+	gpiochip_enable_irq(chip, offset);
+	idio16gpio->irq_mask |= BIT(offset);
 
 	if (!prev_irq_mask) {
 		raw_spin_lock_irqsave(&idio16gpio->lock, flags);
@@ -217,12 +219,14 @@ static int idio_16_irq_set_type(struct irq_data *data, unsigned int flow_type)
 	return 0;
 }
 
-static struct irq_chip idio_16_irqchip = {
+static const struct irq_chip idio_16_irqchip = {
 	.name = "104-idio-16",
 	.irq_ack = idio_16_irq_ack,
 	.irq_mask = idio_16_irq_mask,
 	.irq_unmask = idio_16_irq_unmask,
-	.irq_set_type = idio_16_irq_set_type
+	.irq_set_type = idio_16_irq_set_type,
+	.flags = IRQCHIP_IMMUTABLE,
+	GPIOCHIP_IRQ_RESOURCE_HELPERS,
 };
 
 static irqreturn_t idio_16_irq_handler(int irq, void *dev_id)
@@ -299,7 +303,7 @@ static int idio_16_probe(struct device *dev, unsigned int id)
 	idio16gpio->out_state = 0xFFFF;
 
 	girq = &idio16gpio->chip.irq;
-	girq->chip = &idio_16_irqchip;
+	gpio_irq_chip_set_chip(girq, &idio_16_irqchip);
 	/* This will let us handle the parent IRQ in the driver */
 	girq->parent_handler = NULL;
 	girq->num_parents = 0;