usb: ether: Fix error handling in usb_ether_init

The code checks the return value from uclass_first_device as well as
that the device exists but it passes on the return value which may be
zero if there are no gadget devices. Just check that a device was
returned and return -ENODEV otherwise.

Also remove the dev variable which is not really used for anything.

Signed-off-by: Michal Suchanek <msuchanek@suse.de>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/usb/gadget/ether.c b/drivers/usb/gadget/ether.c
index 6ce389d..43aec7f 100644
--- a/drivers/usb/gadget/ether.c
+++ b/drivers/usb/gadget/ether.c
@@ -2636,18 +2636,17 @@
 
 int usb_ether_init(void)
 {
-	struct udevice *dev;
 	struct udevice *usb_dev;
 	int ret;
 
-	ret = uclass_first_device(UCLASS_USB_GADGET_GENERIC, &usb_dev);
-	if (!usb_dev || ret) {
+	uclass_first_device(UCLASS_USB_GADGET_GENERIC, &usb_dev);
+	if (!usb_dev) {
 		pr_err("No USB device found\n");
-		return ret;
+		return -ENODEV;
 	}
 
-	ret = device_bind_driver(usb_dev, "usb_ether", "usb_ether", &dev);
-	if (!dev || ret) {
+	ret = device_bind_driver(usb_dev, "usb_ether", "usb_ether", NULL);
+	if (ret) {
 		pr_err("usb - not able to bind usb_ether device\n");
 		return ret;
 	}