MIPS: Fix for r24501.

BUG=
R=akos.palfi@imgtec.com

Review URL: https://codereview.chromium.org/646863003

Patch from Paul Lind <paul.lind@imgtec.com>.

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24516 ce2b1a6d-e550-0410-aec6-3dcde31c8c00