radv: Do an early check of distance in triangle culling.

radv: Do an early check of distance in triangle culling.

Culls like 99% of the triangles that are culled at all.

Reduces VALU usage in Q2RTX traversal by ~8%, though doesn't look
like VALU is a bottleneck at this point ...

For Control we get a ~5% reduction in VALU usage, but similarly it
doesn't look like a bottleneck.

Reviewed-by: Konstantin Seurer <konstantin.seurer@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/18830>