usb: gadget: rndis: fix Missing req->context assignment

It is crucial to assign each req->context value to struct rndis.

The problem happens for multi function gadget (g_multi) when multiple
functions are calling common usb_composite_dev control request.

It might happen that *_setup method from one usb function will
alter some fields of this common request issued by other USB
function.
Signed-off-by: Lukasz Majewski <l.majewski@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/gadget/f_rndis.c

@@ -500,6 +500,7 @@ rndis_setup(struct usb_function *f, const struct usb_ctrlrequest *ctrl)
 			if (buf) {
 				memcpy(req->buf, buf, n);
 				req->complete = rndis_response_complete;
+				req->context = rndis;
 				rndis_free_response(rndis->config, buf);
 				value = n;
 			}