winsys/amdgpu: rework the VM alignment optimizations

- don't increase the alignment past 2 MB
- apply the second tweak to older chips too

Acked-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/7055>
1 file changed