PCI: dra7xx: Propagate platform_get_irq() errors in dra7xx_pcie_probe()

platform_get_irq() returns an error code, but the pci-dra7xx driver ignores
it and always returns -EINVAL. This is not correct and prevents
-EPROBE_DEFER from being propagated properly.

Print and propagate the return value of platform_get_irq() on failure.

This issue was detected with the help of Coccinelle.
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Kishon Vijay Abraham I <kishon@ti.com>

drivers/pci/dwc/pci-dra7xx.c

@@ -616,8 +616,8 @@ static int __init dra7xx_pcie_probe(struct platform_device *pdev)
 
 	irq = platform_get_irq(pdev, 0);
 	if (irq < 0) {
-		dev_err(dev, "missing IRQ resource\n");
-		return -EINVAL;
+		dev_err(dev, "missing IRQ resource: %d\n", irq);
+		return irq;
 	}
 
 	res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "ti_conf");