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/gadget/udc/s3c2410_udc.c

@@ -1541,8 +1541,7 @@ static int s3c2410_vbus_draw(struct usb_gadget *_gadget, unsigned ma)
 
 static int s3c2410_udc_start(struct usb_gadget *g,
 		struct usb_gadget_driver *driver);
-static int s3c2410_udc_stop(struct usb_gadget *g,
-		struct usb_gadget_driver *driver);
+static int s3c2410_udc_stop(struct usb_gadget *g);
 
 static const struct usb_gadget_ops s3c2410_ops = {
 	.get_frame		= s3c2410_udc_get_frame,
@@ -1683,8 +1682,7 @@ static int s3c2410_udc_start(struct usb_gadget *g,
 	return 0;
 }
 
-static int s3c2410_udc_stop(struct usb_gadget *g,
-		struct usb_gadget_driver *driver)
+static int s3c2410_udc_stop(struct usb_gadget *g)
 {
 	struct s3c2410_udc *udc = to_s3c2410(g);