net: usb: set error code when usb_alloc_urb fails

In function lan78xx_probe(), variable ret takes the errno code on
failures. However, when the call to usb_alloc_urb() fails, its value
will keeps 0. 0 indicates success in the context, which is inconsistent
with the execution result. This patch fixes the bug, assigning
"-ENOMEM" to ret when usb_alloc_urb() returns a NULL pointer.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=188771

Signed-off-by: Pan Bian <bianpan2016@163.com>
Acked-by: Woojung Huh <woojung.huh@microchip.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/usb/lan78xx.c

@@ -3395,6 +3395,7 @@ static int lan78xx_probe(struct usb_interface *intf,
 	if (buf) {
 		dev->urb_intr = usb_alloc_urb(0, GFP_KERNEL);
 		if (!dev->urb_intr) {
+			ret = -ENOMEM;
 			kfree(buf);
 			goto out3;
 		} else {