ac/nir/cull: Accept NaN and +/- Inf in face culling.
When the determinant that we use for calculating triangle area is NaN, it's not possible to determine the facing of the triangle.
This can happen when a coordinate of one of the triangle's vertices is INFINITY. It's better to just accept these triangles in the shader and let the PA deal with them.
Let's do the same for +/- Inf (though we haven't encountered that yet).