nir: Make rq_load committed src an index

committed has to be a constant so there is no need to have a src and
depend on constant folding to remove the i2b.

Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
Acked-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/22963>

src/intel/compiler/brw_nir_lower_ray_queries.c

@@ -348,7 +348,7 @@ lower_ray_query_intrinsic(nir_builder *b,
    }
 
    case nir_intrinsic_rq_load: {
-      const bool committed = nir_src_as_bool(intrin->src[1]);
+      const bool committed = nir_intrinsic_committed(intrin);
 
       struct brw_nir_rt_mem_ray_defs world_ray_in = {};
       struct brw_nir_rt_mem_ray_defs object_ray_in = {};