Fix fuzzer-found error where left and right were the same register in bitops.

test/mjsunit/regress/bitops-register-alias.js

+// Copyright 2010 the V8 project authors. All rights reserved.
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+
+// Test that the code generator can cope with left and right being in
+// the same register for bitops.
+function f() { for (var i = 10; i < 100; i++) { return i | i; } }
+assertEquals(10, f());