[media] v4l: omap3isp: Fix handling platform_get_irq result

The function can return negative value.

The problem has been detected using proposed semantic patch
scripts/coccinelle/tests/assign_signed_to_unsigned.cocci [1].

[1]: http://permalink.gmane.org/gmane.linux.kernel/2046107Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

drivers/media/platform/omap3isp/isp.c

@@ -2528,12 +2528,13 @@ static int isp_probe(struct platform_device *pdev)
 	}
 
 	/* Interrupt */
-	isp->irq_num = platform_get_irq(pdev, 0);
-	if (isp->irq_num <= 0) {
+	ret = platform_get_irq(pdev, 0);
+	if (ret <= 0) {
 		dev_err(isp->dev, "No IRQ resource\n");
 		ret = -ENODEV;
 		goto error_iommu;
 	}
+	isp->irq_num = ret;
 
 	if (devm_request_irq(isp->dev, isp->irq_num, isp_isr, IRQF_SHARED,
 			     "OMAP3 ISP", isp)) {