Revert "Optimize the emitted instruction of random function for X64"

This reverts r13393.

Review URL: https://codereview.chromium.org/11967009

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@13396 ce2b1a6d-e550-0410-aec6-3dcde31c8c00