i965: Don't minify depth when setting up cube map miptrees on Gen4.

i965: Don't minify depth when setting up cube map miptrees on Gen4.

Prior to Ironlake, cube maps were stored as 3D textures.  In recent
refactoring, we removed a separate "layers" parameter in favor of using
depth.  Unfortunately, depth was getting minified, which is only correct
for actual 3D textures.

Fixes piglit tests:
- bugs/crash-cubemap-order
- fbo/fbo-cubemap
- texturing/cubemap

Also changes texturing/cubemap npot from abort to fail.

This hasn't seen a full test run since Piglit on Mesa master hangs
GM45 a lot.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Eric Anholt <eric@anholt.net>