X87: Fixed flooring division by a power of 2, once again...

port r21769

original message:
    Avoid right shifts by zero bits: On ARM it actually means shifting by
    32 bits (correctness issue) and on other platforms they are useless
    (performance issue). This is fix for the fix in r20544.

    BUG=v8:3259
    LOG=y
R=weiliang.lin@intel.com

Review URL: https://codereview.chromium.org/330133004

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@21829 ce2b1a6d-e550-0410-aec6-3dcde31c8c00