irqchip/renesas-intc-irqpin: Use platform_get_irq_optional() to get the interrupt

platform_get_resource(pdev, IORESOURCE_IRQ, ..) relies on static
allocation of IRQ resources in DT core code, this causes an issue
when using hierarchical interrupt domains using "interrupts" property
in the node as this bypassed the hierarchical setup and messed up the
irq chaining.

In preparation for removal of static setup of IRQ resource from DT core
code use platform_get_irq_optional().
Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20211216182121.5323-1-prabhakar.mahadev-lad.rj@bp.renesas.com

drivers/irqchip/irq-renesas-intc-irqpin.c

@@ -375,7 +375,6 @@ static int intc_irqpin_probe(struct platform_device *pdev)
 	struct intc_irqpin_priv *p;
 	struct intc_irqpin_iomem *i;
 	struct resource *io[INTC_IRQPIN_REG_NR];
-	struct resource *irq;
 	struct irq_chip *irq_chip;
 	void (*enable_fn)(struct irq_data *d);
 	void (*disable_fn)(struct irq_data *d);
@@ -418,12 +417,14 @@ static int intc_irqpin_probe(struct platform_device *pdev)
 
 	/* allow any number of IRQs between 1 and INTC_IRQPIN_MAX */
 	for (k = 0; k < INTC_IRQPIN_MAX; k++) {
-		irq = platform_get_resource(pdev, IORESOURCE_IRQ, k);
-		if (!irq)
+		ret = platform_get_irq_optional(pdev, k);
+		if (ret == -ENXIO)
 			break;
+		if (ret < 0)
+			goto err0;
 
 		p->irq[k].p = p;
-		p->irq[k].requested_irq = irq->start;
+		p->irq[k].requested_irq = ret;
 	}
 
 	nirqs = k;