MIPS: Add OWNERS file for compiler unittests.

BUG=
R=bmeurer@chromium.org

Review URL: https://codereview.chromium.org/648413003

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

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24574 ce2b1a6d-e550-0410-aec6-3dcde31c8c00