drm/virtio: fix a wait_event condition

outcnt may be greater than 1 since commit e1218b8c ("drm/virtio:
Use vmalloc for command buffer allocations.").

Fixes: e1218b8c ("drm/virtio: Use vmalloc for command buffer allocations.")
Signed-off-by: Chia-I Wu <olvaffe@gmail.com>
Cc: David Riley <davidriley@chromium.org>
Link: http://patchwork.freedesktop.org/patch/msgid/20200205181955.202485-2-olvaffe@gmail.comSigned-off-by: Gerd Hoffmann <kraxel@redhat.com>

drivers/gpu/drm/virtio/virtgpu_vq.c

@@ -391,7 +391,8 @@ static void virtio_gpu_queue_fenced_ctrl_buffer(struct virtio_gpu_device *vgdev,
 	 */
 	if (vq->num_free < 2 + outcnt) {
 		spin_unlock(&vgdev->ctrlq.qlock);
-		wait_event(vgdev->ctrlq.ack_queue, vq->num_free >= 3);
+		wait_event(vgdev->ctrlq.ack_queue,
+			   vq->num_free >= 2 + outcnt);
 		goto again;
 	}