anv/pipeline: Do less deref instruction lowering

anv/pipeline: Do less deref instruction lowering

This commit removes most of the deref instruction lowering.  Instead of
lowering early, we only lower textures and images and we only do so
right before any of the anv image lowering passes.

Acked-by: Rob Clark <robdclark@gmail.com>
Acked-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
Acked-by: Dave Airlie <airlied@redhat.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>