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>

drivers/usb/dwc2/gadget.c

@@ -2921,8 +2921,7 @@ err:
  *
  * Stop udc hw block and stay tunned for future transmissions
  */
-static int s3c_hsotg_udc_stop(struct usb_gadget *gadget,
-			  struct usb_gadget_driver *driver)
+static int s3c_hsotg_udc_stop(struct usb_gadget *gadget)
 {
 	struct s3c_hsotg *hsotg = to_hsotg(gadget);
 	unsigned long flags = 0;