[ic][mips][mips64] Ensure store handlers return value in proper register.

test/mjsunit/regress/regress-crbug-650973.js

 // Copyright 2016 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
 
-Array.prototype.__proto__ = null;
-var prototype = Array.prototype;
+var v = {p:0};
+// Turn the object into dictionary mode.
+v.__defineGetter__("p", function() { return 13; });
+
 function f() {
-  prototype.lastIndexOf({});
+  var boom = (v.foo = v);
+  assertEquals(v, boom.foo);
 }
+
 f();
 f();
-%OptimizeFunctionOnNextCall(f);
 f();