lavapipe: Use generated command queue code

lavapipe: Use generated command queue code

Most of the code that implements entry points for commands doesn't need
to be manually written. So just drop it.

Signed-off-by: Tomeu Vizoso <tomeu.vizoso@collabora.com>
Reviewed-by: Antonio Caggiano <antonio.caggiano@collabora.com>
Acked-By: Mike Blumenkrantz <michael.blumenkrantz@gmail.com>
Reviewed-by: Dave Airlie <airlied@redhat.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/12369>