intel/nir: Zero local index const struct for valgrind & nir_serialize

Signed-off-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Timothy Arceri <tarceri@itsqueeze.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>

src/intel/compiler/brw_nir_lower_cs_intrinsics.c

@@ -116,6 +116,7 @@ lower_cs_intrinsics_convert_block(struct lower_intrinsics_state *state,
          nir_ssa_def *local_index = nir_load_local_invocation_index(b);
 
          nir_const_value uvec3;
+         memset(&uvec3, 0, sizeof(uvec3));
          uvec3.u32[0] = 1;
          uvec3.u32[1] = size[0];
          uvec3.u32[2] = size[0] * size[1];