agx: Assert vertex_id, instance_id are VS-only
What does this MR do and why?
agx: Assert vertex_id, instance_id are VS-only
We can get them in other shaders transiently due to merging shader stages, but they need to be lowered since the hardware versions only exist in the hardware VS. So the compiler should never see them outside VS.
Signed-off-by: Alyssa Rosenzweig alyssa@rosenzweig.io