nir: Zero local_size 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/compiler/nir/nir_lower_system_values.c

@@ -58,6 +58,7 @@ convert_block(nir_block *block, nir_builder *b)
           */
 
          nir_const_value local_size;
+         memset(&local_size, 0, sizeof(local_size));
          local_size.u32[0] = b->shader->info.cs.local_size[0];
          local_size.u32[1] = b->shader->info.cs.local_size[1];
          local_size.u32[2] = b->shader->info.cs.local_size[2];