radv: Disable NGG for GS with suboptimal output vertex count.

radv: Disable NGG for GS with suboptimal output vertex count.

When GS has a lot of output vertices: In this case,
the occupancy of NGG GS is very low because API GS invocations
can't even occupy a single Wave32 wave.
Therefore the legacy pipeline performs better here.

Cc: mesa-stable
Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/6260
Signed-off-by: Timur Kristóf <timur.kristof@gmail.com>
Reviewed-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/15767>