MIPS: Fix compilation with clang.

Port r18267 (12a613f)

BUG=
R=gergely@homejinni.com

Review URL: https://codereview.chromium.org/98403003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@18268 ce2b1a6d-e550-0410-aec6-3dcde31c8c00