vhost: actually track log eventfd file

While reviewing vhost log code, I found out that log_file is never
set. Note: I haven't tested the change (QEMU doesn't use LOG_FD yet).

Cc: stable@vger.kernel.org
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
void vhost_work_queue(struct vhost_dev *dev, struct vhost_work *work)
{
	unsigned long flags;

	spin_lock_irqsave(&dev->work_lock, flags);
	if (list_empty(&work->node)) {
		list_add_tail(&work->node, &dev->work_list);
		work->queue_seq++;
		spin_unlock_irqrestore(&dev->work_lock, flags);
		wake_up_process(dev->worker);
	} else {
		spin_unlock_irqrestore(&dev->work_lock, flags);
	}
}

void vhost_work_queue(struct vhost_dev *dev, struct vhost_work *work)
{
	unsigned long flags;

	spin_lock_irqsave(&dev->work_lock, flags);
	if (list_empty(&work->node)) {
		list_add_tail(&work->node, &dev->work_list);
		work->queue_seq++;
		spin_unlock_irqrestore(&dev->work_lock, flags);
		wake_up_process(dev->worker);
	} else {
		spin_unlock_irqrestore(&dev->work_lock, flags);
	}
}
