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/at91_udc.c b/drivers/usb/gadget/udc/at91_udc.c
index 5c4cede..f47f16c 100644
--- a/drivers/usb/gadget/udc/at91_udc.c
+++ b/drivers/usb/gadget/udc/at91_udc.c
@@ -984,8 +984,8 @@
 
 static int at91_start(struct usb_gadget *gadget,
 		struct usb_gadget_driver *driver);
-static int at91_stop(struct usb_gadget *gadget,
-		struct usb_gadget_driver *driver);
+static int at91_stop(struct usb_gadget *gadget);
+
 static const struct usb_gadget_ops at91_udc_ops = {
 	.get_frame		= at91_get_frame,
 	.wakeup			= at91_wakeup,
@@ -1644,8 +1644,7 @@
 	return 0;
 }
 
-static int at91_stop(struct usb_gadget *gadget,
-		struct usb_gadget_driver *driver)
+static int at91_stop(struct usb_gadget *gadget)
 {
 	struct at91_udc *udc;
 	unsigned long	flags;