cdc-acm: cleanup debugging in submission path

Actually make it retutn useful information.

Signed-off-by: Oliver Neukum <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/usb/class/cdc-acm.c

···
 	if (!test_and_clear_bit(index, &acm->read_urbs_free))
 		return 0;
 
-	dev_vdbg(&acm->data->dev, "%s - urb %d\n", __func__, index);
-
 	res = usb_submit_urb(acm->read_urbs[index], mem_flags);
 	if (res) {
 		if (res != -EPERM) {
 			dev_err(&acm->data->dev,
-					"%s - usb_submit_urb failed: %d\n",
-					__func__, res);
+					"urb %d failed submission with %d\n",
+					index, res);
 		}
 		set_bit(index, &acm->read_urbs_free);
 		return res;
+	} else {
+		dev_vdbg(&acm->data->dev, "submitted urb %d\n", index);
 	}
 
 	return 0;