Revert "GVN fix, preventing loads hoisting above stores to the same field when HObjectAccess's repr…

test/mjsunit/regress/regress-gvn-ftt.js

-// Copyright 2014 the V8 project authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-// Flags: --allow-natives-syntax --track-field-types --use-gvn
-
-function A(id) {
-  this.id = id;
-}
-
-var a1 = new A(1);
-var a2 = new A(2);
-
-
-var g;
-function f(o, value) {
-  g = o.o;
-  o.o = value;
-  return o.o;
-}
-
-var obj = {o: a1};
-
-f(obj, a1);
-f(obj, a1);
-%OptimizeFunctionOnNextCall(f);
-assertEquals(a2.id, f(obj, a2).id);