virtio-console: call scheduler when we free unused buffs

For virtio-net we were getting CPU stall warnings, and fixed it by
calling the scheduler: see f8bb5104 ("virtio_net: suppress cpu stall
when free_unused_bufs").

This driver is similar so theoretically the same logic applies.
Signed-off-by: Xianting Tian <xianting.tian@linux.alibaba.com>
Message-Id: <20230609131817.712867-3-xianting.tian@linux.alibaba.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

drivers/char/virtio_console.c

@@ -1935,6 +1935,7 @@ static void remove_vqs(struct ports_device *portdev)
 		flush_bufs(vq, true);
 		while ((buf = virtqueue_detach_unused_buf(vq)))
 			free_buf(buf, true);
+		cond_resched();
 	}
 	portdev->vdev->config->del_vqs(portdev->vdev);
 	kfree(portdev->in_vqs);