radv: Disable NGG culling when conservative overestimation is used.

radv: Disable NGG culling when conservative overestimation is used.

Even when small primitive culling is disabled, the face culling algorithm
in ac_nir_cull can delete tiny triangles when their area is almost zero.

Cc: mesa-stable
Signed-off-by: Timur Kristóf <timur.kristof@gmail.com>
Reviewed-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/20987>
(cherry picked from commit 3508597aa1b88d1b5a6f78ad53d8abcc32cde2c9)