[turbofan] Fix typo in IA-32 code generator.

TEST=benchmarks/octane/zlib
TBR=jarin@chromium.org

Review URL: https://codereview.chromium.org/633373002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24461 ce2b1a6d-e550-0410-aec6-3dcde31c8c00