gpio: grgpio: Make irq_chip immutable

Kernel warns about mutable irq_chips:
"not an immutable chip, please consider fixing!"

Constify grgpio_irq_chip, flag the irq_chip as IRQCHIP_IMMUTABLE, add the
new helper functions, and call the appropriate gpiolib functions.

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-v1-2-639377c98288@nxp.com
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

Author: MrVan

drivers/gpio/gpio-grgpio.c

@@ -170,6 +170,8 @@ static void grgpio_irq_mask(struct irq_data *d)
 	grgpio_set_imask(priv, offset, 0);
 
 	raw_spin_unlock_irqrestore(&priv->gc.bgpio_lock, flags);
+
+	gpiochip_disable_irq(&priv->gc, d->hwirq);
 }
 
 static void grgpio_irq_unmask(struct irq_data *d)
@@ -178,18 +180,21 @@ static void grgpio_irq_unmask(struct irq_data *d)
 	int offset = d->hwirq;
 	unsigned long flags;
 
+	gpiochip_enable_irq(&priv->gc, d->hwirq);
 	raw_spin_lock_irqsave(&priv->gc.bgpio_lock, flags);
 
 	grgpio_set_imask(priv, offset, 1);
 
 	raw_spin_unlock_irqrestore(&priv->gc.bgpio_lock, flags);
 }
 
-static struct irq_chip grgpio_irq_chip = {
+static const struct irq_chip grgpio_irq_chip = {
 	.name			= "grgpio",
 	.irq_mask		= grgpio_irq_mask,
 	.irq_unmask		= grgpio_irq_unmask,
 	.irq_set_type		= grgpio_irq_set_type,
+	.flags = IRQCHIP_IMMUTABLE,
+	GPIOCHIP_IRQ_RESOURCE_HELPERS,
 };
 
 static irqreturn_t grgpio_irq_handler(int irq, void *dev)