[media] media: am437x-vpfe: 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/2046107

Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

drivers/media/platform/am437x/am437x-vpfe.c

@@ -2551,11 +2551,12 @@ static int vpfe_probe(struct platform_device *pdev)
 	if (IS_ERR(ccdc->ccdc_cfg.base_addr))
 		return PTR_ERR(ccdc->ccdc_cfg.base_addr);
 
-	vpfe->irq = platform_get_irq(pdev, 0);
-	if (vpfe->irq <= 0) {
+	ret = platform_get_irq(pdev, 0);
+	if (ret <= 0) {
 		dev_err(&pdev->dev, "No IRQ resource\n");
 		return -ENODEV;
 	}
+	vpfe->irq = ret;
 
 	ret = devm_request_irq(vpfe->pdev, vpfe->irq, vpfe_isr, 0,
 			       "vpfe_capture0", vpfe);