usb: gadget: at91_udc: fix endpoint descriptor dereference

The patch 5a6506f0 (Update at91_udc to use usb_endpoint_descriptor inside the
struct usb_ep) removes the desc field of struct at91_ep. This convertion had
not been completed which leads to a compilation error.
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Acked-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/gadget/at91_udc.c

@@ -475,7 +475,7 @@ static int at91_ep_enable(struct usb_ep *_ep,
 	unsigned long	flags;
 
 	if (!_ep || !ep
-			|| !desc || ep->desc
+			|| !desc || ep->ep.desc
 			|| _ep->name == ep0name
 			|| desc->bDescriptorType != USB_DT_ENDPOINT
 			|| (maxpacket = usb_endpoint_maxp(desc)) == 0