Improves some V8 benchmarks by a few % on A9.

Patch by ARM Ltd.

BUG=none
TEST=Added to test-assembler-arm.cc.

Review URL: http://codereview.chromium.org/6874010

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@7647 ce2b1a6d-e550-0410-aec6-3dcde31c8c00