st/mesa: Fix assertions for copying texture image to finalized miptree.

st/mesa: Fix assertions for copying texture image to finalized miptree.

The layer dimension of array textures is not subject to mipmap minification.
OTOH we were missing an assertion for the depth dimension.

Fixes assertion failures with piglit {f,v}s-textureSize-sampler1DArrayShadow.
For some reason, they only resulted in piglit 'warn' results for me, not
failures.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=56211

NOTE: This is a candidate for the stable branches.

Signed-off-by: Michel Dänzer <michel.daenzer@amd.com>
Reviewed-by: Brian Paul <brianp@vmware.com>
Tested-by: Andreas Boll <andreas.boll.dev@gmail.com>