MIPS: fix arm simulator after 14725

Port r14731 (046b5d8d)

BUG=

Review URL: https://codereview.chromium.org/15606002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@14737 ce2b1a6d-e550-0410-aec6-3dcde31c8c00