i965/miptree: Add an intel_tiling_supports_hiz helper

i965/miptree: Add an intel_tiling_supports_hiz helper

We need this split for the same reason that we need the split for CCS:
intel_miptree_supports_hiz is called *before* we choose the actual
tiling.  Adding a tiling_supports_hiz helper lets choose_aux_usage
more accurately decide whether or not to enable hiz.  In particular,
this prevents us from enabling HiZ on linear depth buffers.

Reviewed-by: Topi Pohjolainen <topi.pohjolainen@intel.com>