usb: gadget: f_midi: check for error on usb_ep_queue

f_midi is not checking whether there is an error on usb_ep_queue
request, ignoring potential problems, such as memory leaks.
Signed-off-by: Felipe F. Tonello <eu@felipetonello.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/gadget/function/f_midi.c

@@ -547,10 +547,16 @@ static void f_midi_transmit(struct f_midi *midi, struct usb_request *req)
 		}
 	}
 
-	if (req->length > 0)
-		usb_ep_queue(ep, req, GFP_ATOMIC);
-	else
+	if (req->length > 0) {
+		int err;
+
+		err = usb_ep_queue(ep, req, GFP_ATOMIC);
+		if (err < 0)
+			ERROR(midi, "%s queue req: %d\n",
+			      midi->in_ep->name, err);
+	} else {
 		free_ep_req(ep, req);
+	}
 }
 
 static void f_midi_in_tasklet(unsigned long data)