cdc-ether: usbnet_cdc_zte_status() can be static

Fixes the following sparse warning:

drivers/net/usb/cdc_ether.c:469:6: warning:
 symbol 'usbnet_cdc_zte_status' was not declared. Should it be static?
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/usb/cdc_ether.c

@@ -466,7 +466,7 @@ static int usbnet_cdc_zte_rx_fixup(struct usbnet *dev, struct sk_buff *skb)
  * connected. This causes the link state to be incorrect. Work around this by
  * always setting the state to off, then on.
  */
-void usbnet_cdc_zte_status(struct usbnet *dev, struct urb *urb)
+static void usbnet_cdc_zte_status(struct usbnet *dev, struct urb *urb)
 {
 	struct usb_cdc_notification *event;