usb: gadget: s3c2410_udc: fix error return code in s3c2410_udc_probe()

Fix to return a negative error code in the gpio_to_irq() error handling
case instead of 0, as done elsewhere in this function.
Reviewed-by: NJingoo Han <jg1.han@samsung.com>
Signed-off-by: NWei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: NFelipe Balbi <balbi@ti.com>

drivers/usb/gadget/s3c2410_udc.c

@@ -1851,6 +1851,7 @@ static int s3c2410_udc_probe(struct platform_device *pdev)
 		irq = gpio_to_irq(udc_info->vbus_pin);
 		if (irq < 0) {
 			dev_err(dev, "no irq for gpio vbus pin\n");
+			retval = irq;
 			goto err_gpio_claim;
 		}