MIPS64: Fix simulator arguments handling on generated code entry.

Removed workaround for this issue.

TEST=mjsunit, cctest on sim64
BUG=
R=paul.lind@imgtec.com

Review URL: https://codereview.chromium.org/695933002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@25043 ce2b1a6d-e550-0410-aec6-3dcde31c8c00