[media] staging: media: omap4iss: 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/staging/media/omap4iss/iss.c

@@ -1440,12 +1440,13 @@ static int iss_probe(struct platform_device *pdev)
 		 iss_reg_read(iss, OMAP4_ISS_MEM_ISP_SYS1, ISP5_REVISION));
 
 	/* Interrupt */
-	iss->irq_num = platform_get_irq(pdev, 0);
-	if (iss->irq_num <= 0) {
+	ret = platform_get_irq(pdev, 0);
+	if (ret <= 0) {
 		dev_err(iss->dev, "No IRQ resource\n");
 		ret = -ENODEV;
 		goto error_iss;
 	}
+	iss->irq_num = ret;
 
 	if (devm_request_irq(iss->dev, iss->irq_num, iss_isr, IRQF_SHARED,
 			     "OMAP4 ISS", iss)) {