staging: iio: adc: fix error return code in ad7606_par_probe()

platform_get_irq() returns an error code, but the ad7606_par driver
ignores it and always returns -ENODEV. 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: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/staging/iio/adc/ad7606_par.c

@@ -57,8 +57,8 @@ static int ad7606_par_probe(struct platform_device *pdev)
 
 	irq = platform_get_irq(pdev, 0);
 	if (irq < 0) {
-		dev_err(&pdev->dev, "no irq\n");
-		return -ENODEV;
+		dev_err(&pdev->dev, "no irq: %d\n", irq);
+		return irq;
 	}
 
 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);