drm/virtio: move the check for vqs_ready earlier

When vqs_ready is false, vq should be considered invalid and we
should not check vq->num_free.  After this change, a fenced command
queued before the vqs are ready will have fence id 0 and will be
considered done.

Signed-off-by: Chia-I Wu <olvaffe@gmail.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20200205181955.202485-9-olvaffe@gmail.com


Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>