MIPS: Orthogonalize Lithium binary op instructions.

Port r16739 (cd8e4a21)

BUG=
R=gergely@homejinni.com

Review URL: https://codereview.chromium.org/23494054

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@16743 ce2b1a6d-e550-0410-aec6-3dcde31c8c00