drbd: Avoid inconsistent locking warning

request_timer_fn() takes resource->req_lock via the device and releases it via
the connection.  Avoid this as it is confusing static code checkers.
Reported-by: "Dan Carpenter" <dan.carpenter@oracle.com>
Signed-off-by: Andreas Gruenbacher <agruen@linbit.com>
Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

drivers/block/drbd/drbd_req.c

@@ -1645,6 +1645,6 @@ void request_timer_fn(unsigned long data)
 		? oldest_submit_jif + dt : now + et;
 	nt = time_before(ent, dt) ? ent : dt;
 out:
-	spin_unlock_irq(&connection->resource->req_lock);
+	spin_unlock_irq(&device->resource->req_lock);
 	mod_timer(&device->request_timer, nt);
 }