mfd: Prevent unassigned pointer from being used in ab8500-gpadc driver

Before this patch if probe failed to find the platform IRQ it
would attempt to print a message out using dev_err, which in
turn was being passed an unassigned pointer. This patch
ensures the information passed to dev_err is correct.
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

drivers/mfd/ab8500-gpadc.c

@@ -584,7 +584,7 @@ static int __devinit ab8500_gpadc_probe(struct platform_device *pdev)
 
 	gpadc->irq = platform_get_irq_byname(pdev, "SW_CONV_END");
 	if (gpadc->irq < 0) {
-		dev_err(gpadc->dev, "failed to get platform irq-%d\n",
+		dev_err(&pdev->dev, "failed to get platform irq-%d\n",
 			gpadc->irq);
 		ret = gpadc->irq;
 		goto fail;