Fix potential register trampling in JIT since r157313.
https://bugs.webkit.org/show_bug.cgi?id=122691

Patch by Julien Brianceau <jbriance@cisco.com> on 2013-10-12
Reviewed by Michael Saboff.

* jit/CCallHelpers.h:
(JSC::CCallHelpers::setupArgumentsWithExecState):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@157339 268f45cc-cd09-0410-ab3c-d52691b4dbfc