radeonsi: pack LDS better for NGG culling

There is a barrier between lds_pos_cull_* use and lds_pos_* use, so they
can occupy the same LDS space.

Acked-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/7172>
1 file changed