freedreno/a6xx: fix 3d tex layout

Fixes dEQP-GLES3.functional.texture.specification.texstorage3d.size.3d_2x2x2_2_levels

Signed-off-by: Rob Clark <robdclark@chromium.org>
Reviewed-by: Kristian H. Kristensen <hoegsberg@google.com>
22 jobs for !1925 with wip/a6xx-3dlayout in 20 minutes and 54 seconds (queued for 1 minute and 39 seconds)
merge request