The change removes one unused multiply and reschedules
the shift, multiply and jump instructions to reduce
stall. Experiment shows it improve about 20% performance
on x64 for exponetials from about 100 to 2000.

Review URL: https://chromiumcodereview.appspot.com/10939013
Patch from Xi Qian <xi.qian@intel.com>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@12535 ce2b1a6d-e550-0410-aec6-3dcde31c8c00