anv: Use isl_aux_state for HiZ resolves

anv: Use isl_aux_state for HiZ resolves

Rather than looking at the aux usage, we look at the isl_aux_state which
provides us with more detailed information.  This commit adds a couple
helpers to isl which let us quickly determine if we have valid depth/hiz
on the initial layout and if we need valid depth/hiz for the final
layout.

Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Reviewed-by: Nanley Chery <nanley.g.chery@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/2605>