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/chipidea/udc.c b/drivers/usb/chipidea/udc.c
index 0444d3f..f4397b2 100644
--- a/drivers/usb/chipidea/udc.c
+++ b/drivers/usb/chipidea/udc.c
@@ -1544,8 +1544,7 @@
 
 static int ci_udc_start(struct usb_gadget *gadget,
 			 struct usb_gadget_driver *driver);
-static int ci_udc_stop(struct usb_gadget *gadget,
-			struct usb_gadget_driver *driver);
+static int ci_udc_stop(struct usb_gadget *gadget);
 /**
  * Device operations part of the API to the USB controller hardware,
  * which don't involve endpoints (or i/o)
@@ -1682,8 +1681,7 @@
 /**
  * ci_udc_stop: unregister a gadget driver
  */
-static int ci_udc_stop(struct usb_gadget *gadget,
-			struct usb_gadget_driver *driver)
+static int ci_udc_stop(struct usb_gadget *gadget)
 {
 	struct ci_hdrc *ci = container_of(gadget, struct ci_hdrc, gadget);
 	unsigned long flags;