intel/compiler: call nir_opt_dead_cf() after we have finished all opts

This will avoid a regression with the following patch.

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/597>

src/intel/compiler/brw_nir.c

@@ -1192,6 +1192,7 @@ brw_postprocess_nir(nir_shader *nir, const struct brw_compiler *compiler,
    OPT(nir_copy_prop);
    OPT(nir_opt_dce);
    OPT(nir_opt_move, nir_move_comparisons);
+   OPT(nir_opt_dead_cf);
 
    OPT(nir_lower_bool_to_int32);
    OPT(nir_copy_prop);