serial: 8250_bcm7271: Use platform_get_irq() 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 bypasses the hierarchical setup and messes up the
irq chaining.

In preparation for removal of static setup of IRQ resource from DT core
code use platform_get_irq().

Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Link: https://lore.kernel.org/r/20211224142917.6966-3-prabhakar.mahadev-lad.rj@bp.renesas.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/8250/8250_bcm7271.c

@@ -941,7 +941,7 @@ static int brcmuart_probe(struct platform_device *pdev)
 	struct brcmuart_priv *priv;
 	struct clk *baud_mux_clk;
 	struct uart_8250_port up;
-	struct resource *irq;
+	int irq;
 	void __iomem *membase = NULL;
 	resource_size_t mapbase = 0;
 	u32 clk_rate = 0;
@@ -952,11 +952,9 @@ static int brcmuart_probe(struct platform_device *pdev)
 		"uart", "dma_rx", "dma_tx", "dma_intr2", "dma_arb"
 	};
 
-	irq = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
-	if (!irq) {
-		dev_err(dev, "missing irq\n");
-		return -EINVAL;
-	}
+	irq = platform_get_irq(pdev, 0);
+	if (irq < 0)
+		return irq;
 	priv = devm_kzalloc(dev, sizeof(struct brcmuart_priv),
 			GFP_KERNEL);
 	if (!priv)
@@ -1044,7 +1042,7 @@ static int brcmuart_probe(struct platform_device *pdev)
 	up.port.dev = dev;
 	up.port.mapbase = mapbase;
 	up.port.membase = membase;
-	up.port.irq = irq->start;
+	up.port.irq = irq;
 	up.port.handle_irq = brcmuart_handle_irq;
 	up.port.regshift = 2;
 	up.port.iotype = of_device_is_big_endian(np) ?