usb: gadget: Refactor request completion

Use the recently introduced usb_gadget_giveback_request() in favor of
direct invocation of the completion routine.

All places in drivers/usb/ matching "[-.]complete(" were replaced with a
call to usb_gadget_giveback_request(). This was compile-tested with all
ARM drivers enabled and runtime-tested for musb.

Signed-off-by: Michal Sojka <sojka@merica.cz>
Acked-by: Felipe Balbi <balbi@ti.com>
Tested-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/gadget/udc/amd5536udc.c

@@ -841,7 +841,7 @@ __acquires(ep->dev->lock)
 		&req->req, req->req.length, ep->ep.name, sts);
 
 	spin_unlock(&dev->lock);
-	req->req.complete(&ep->ep, &req->req);
+	usb_gadget_giveback_request(&ep->ep, &req->req);
 	spin_lock(&dev->lock);
 	ep->halted = halted;
 }