usb_ether: register usb ethernet gadget at each eth init

Since the ether may not be the only one usb gadget would be used
in the uboot, it is neccessary to do the register each time the
eth begin to work to make usb gadget driver less confussed when
we want to use two different usb gadget at the same time.

Usb gadget driver could simple ignore the register operation, if
it find the driver has been registered already.
Signed-off-by: NLei Wen <leiwen@marvell.com>

drivers/usb/gadget/ether.c

@@ -1456,6 +1456,7 @@ static void eth_unbind(struct usb_gadget *gadget)
 /*	unregister_netdev (dev->net);*/
 /*	free_netdev(dev->net);*/
 
+	dev->gadget = NULL;
 	set_gadget_data(gadget, NULL);
 }
 
@@ -1788,6 +1789,8 @@ static int usb_eth_init(struct eth_device *netdev, bd_t *bd)
 		error("received NULL ptr");
 		goto fail;
 	}
+	if (usb_gadget_register_driver(&eth_driver) < 0)
+		goto fail;
 
 	dev->network_started = 0;
 
@@ -1895,7 +1898,12 @@ void usb_eth_halt(struct eth_device *netdev)
 		return;
 	}
 
+	/* If the gadget not registered, simple return */
+	if (!dev->gadget)
+		return;
+
 	usb_gadget_disconnect(dev->gadget);
+	usb_gadget_unregister_driver(&eth_driver);
 }
 
 static struct usb_gadget_driver eth_driver = {
@@ -1957,10 +1965,6 @@ int usb_eth_initialize(bd_t *bi)
 	if (status)
 		goto fail;
 
-	status = usb_gadget_register_driver(&eth_driver);
-	if (status < 0)
-		goto fail;
-
 	eth_register(netdev);
 	return 0;