usbnet: remove usb_get/put_dev in .probe and .disconnect

usb_device is parent device of usb_interface in the view of driver
model, so its reference count is always held during .probe/.disconnect
of usb_interface instance.

This patch just removes the unnecessay usb_get/put_dev.
Signed-off-by: NMing Lei <tom.leiming@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/usb/usbnet.c

@@ -1307,7 +1307,6 @@ void usbnet_disconnect (struct usb_interface *intf)
 	usb_free_urb(dev->interrupt);
 
 	free_netdev(net);
-	usb_put_dev (xdev);
 }
 EXPORT_SYMBOL_GPL(usbnet_disconnect);
 
@@ -1363,8 +1362,6 @@ usbnet_probe (struct usb_interface *udev, const struct usb_device_id *prod)
 	xdev = interface_to_usbdev (udev);
 	interface = udev->cur_altsetting;
 
-	usb_get_dev (xdev);
-
 	status = -ENOMEM;
 
 	// set up our own records
@@ -1493,7 +1490,6 @@ usbnet_probe (struct usb_interface *udev, const struct usb_device_id *prod)
 out1:
 	free_netdev(net);
 out:
-	usb_put_dev(xdev);
 	return status;
 }
 EXPORT_SYMBOL_GPL(usbnet_probe);