usb: gadget: udc: udc-xilinx: Place correct function names into the headers

Fixes the following W=1 kernel build warning(s):

 drivers/usb/gadget/udc/udc-xilinx.c:802: warning: expecting prototype for xudc_ep_enable(). Prototype was for __xudc_ep_enable() instead
 drivers/usb/gadget/udc/udc-xilinx.c:997: warning: expecting prototype for xudc_ep0_queue(). Prototype was for __xudc_ep0_queue() instead

Cc: Felipe Balbi <balbi@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Michal Simek <michal.simek@xilinx.com>
Cc: linux-usb@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20210526130037.856068-20-lee.jones@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/gadget/udc/udc-xilinx.c

@@ -791,7 +791,7 @@ static int xudc_ep_set_halt(struct usb_ep *_ep, int value)
 }
 
 /**
- * xudc_ep_enable - Enables the given endpoint.
+ * __xudc_ep_enable - Enables the given endpoint.
  * @ep: pointer to the xusb endpoint structure.
  * @desc: pointer to usb endpoint descriptor.
  *
@@ -987,7 +987,7 @@ static void xudc_free_request(struct usb_ep *_ep, struct usb_request *_req)
 }
 
 /**
- * xudc_ep0_queue - Adds the request to endpoint 0 queue.
+ * __xudc_ep0_queue - Adds the request to endpoint 0 queue.
  * @ep0: pointer to the xusb endpoint 0 structure.
  * @req: pointer to the xusb request structure.
  *