usb: gadget: remove unnecessary 'driver' argument

now that no UDC driver relies on the extra
'driver' argument to ->udc_stop(), we can
safely remove it.

This commit is based on previous work by
Robert Baldyga <r.baldyga@samsung.com> which
can be found at [1]; however that patch turned
out to have a high probability of regressing
many UDC drivers because of a blind search & replace
s/driver/$udc->driver/ which caused the 'driver'
argument to stop_activity() to be a valid non-NULL
pointer when it should be NULL, thus causing UDCs
to mistakenly call gadget driver's ->disconnect()
callback.

[1] http://markmail.org/message/x5zneg4xea4zntab

Acked-by: Peter Chen <peter.chen@freescale.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>
diff --git a/drivers/usb/gadget/udc/udc-xilinx.c b/drivers/usb/gadget/udc/udc-xilinx.c
index ed27e16..1eac56f 100644
--- a/drivers/usb/gadget/udc/udc-xilinx.c
+++ b/drivers/usb/gadget/udc/udc-xilinx.c
@@ -1403,8 +1403,7 @@
  *
  * Return: zero always
  */
-static int xudc_stop(struct usb_gadget *gadget,
-		     struct usb_gadget_driver *driver)
+static int xudc_stop(struct usb_gadget *gadget)
 {
 	struct xusb_udc *udc = to_udc(gadget);
 	unsigned long flags;