usb: gadget: at91_udc: move the dereference below the NULL test

The dereference should be moved below the NULL test.

spatch with a semantic match is used to found this.
(http://coccinelle.lip6.fr/)

Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/gadget/at91_udc.c

@@ -469,7 +469,7 @@ static int at91_ep_enable(struct usb_ep *_ep,
 				const struct usb_endpoint_descriptor *desc)
 {
 	struct at91_ep	*ep = container_of(_ep, struct at91_ep, ep);
-	struct at91_udc	*udc = ep->udc;
+	struct at91_udc *udc;
 	u16		maxpacket;
 	u32		tmp;
 	unsigned long	flags;
@@ -484,6 +484,7 @@ static int at91_ep_enable(struct usb_ep *_ep,
 		return -EINVAL;
 	}
 
+	udc = ep->udc;
 	if (!udc->driver || udc->gadget.speed == USB_SPEED_UNKNOWN) {
 		DBG("bogus device state\n");
 		return -ESHUTDOWN;