panfrost: Disable point sprites on Bifrost

It doesn't look like the lowering in !6473 will land before the branch
point. Let's nop out point sprites in the backend to avoid MMU faults
from creating invalid Midgard-style varyings.

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/7408>
1 file changed