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/r8a66597-udc.c b/drivers/usb/gadget/udc/r8a66597-udc.c
index f818661..b63a527 100644
--- a/drivers/usb/gadget/udc/r8a66597-udc.c
+++ b/drivers/usb/gadget/udc/r8a66597-udc.c
@@ -1763,8 +1763,7 @@
 	return 0;
 }
 
-static int r8a66597_stop(struct usb_gadget *gadget,
-		struct usb_gadget_driver *driver)
+static int r8a66597_stop(struct usb_gadget *gadget)
 {
 	struct r8a66597 *r8a66597 = gadget_to_r8a66597(gadget);
 	unsigned long flags;