nir: Rework lower_locals_to_regs to use deref instructions

This completely reworks the pass to support deref instructions and
delete support for old deref chains

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>

src/intel/compiler/brw_nir.c

@@ -766,8 +766,6 @@ brw_postprocess_nir(nir_shader *nir, const struct brw_compiler *compiler,
    OPT(nir_opt_dce);
    OPT(nir_opt_move_comparisons);
 
-   OPT(nir_lower_deref_instrs, nir_lower_load_store_derefs);
-
    OPT(nir_lower_locals_to_regs);
 
    if (unlikely(debug_enabled)) {