[arm] Clean up disabling of sharing code target entries.

test/mjsunit/compiler/regress-725743.js

+// Copyright 2017 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: --no-turbo --cache=code --no-lazy
+
+function f() {
+  var n = a.length;
+  for (var i = 0; i < n; i++) {
+  }
+  for (var i = 0; i < n; i++) {
+  }
+}
+var a = "xxxxxxxxxxxxxxxxxxxxxxxxx";
+while (a.length < 100000) a = a + a;
+f();