Always execute the bbox code regardless of negative W, and then simply
use || to discard the result if any W is negative. This is expected to be
rare. (it only happens when a primitive intersects the near plane)
This allows us to eliminate the else statement, which is no longer
executed for accepted primitives with negative W, which are the only
primitives that needed the else branch.
Reviewed-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/11754>
d9173b3b46