winsys/amdgpu: fix radeon_surf::macro_tile_index for imported textures

winsys/amdgpu: fix radeon_surf::macro_tile_index for imported textures

Maybe this is why SDMA has been broken for many amdgpu users?

SDMA is the only block which is used with imported textures and relies
on this variable. DB also uses it, but it doesn't get imported textures,
so it's unaffected.

I do get SDMA failures on Tonga before this patch if R600_DEBUG=testdma
is changed to use imported textures.

Cc: 11.2 12.0 13.0 <mesa-stable@lists.freedesktop.org>
Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
Reviewed-by: Nicolai Hähnle <nicolai.haehnle@amd.com>