util: use C99 declaration in the for-loop set_foreach() macro

Signed-off-by: Eric Engestrom <eric@engestrom.ch>
Reviewed-by: Timothy Arceri <tarceri@itsqueeze.com>

src/compiler/nir/nir_from_ssa.c

@@ -830,7 +830,6 @@ place_phi_read(nir_shader *shader, nir_register *reg,
    if (block != def->parent_instr->block) {
       /* Try to go up the single-successor tree */
       bool all_single_successors = true;
-      struct set_entry *entry;
       set_foreach(block->predecessors, entry) {
          nir_block *pred = (nir_block *)entry->key;
          if (pred->successors[0] && pred->successors[1]) {