ARM: Fix erroneous detection of Double result type in Integer32 BinaryOpStubs

BUG=v8:2648

Review URL: https://codereview.chromium.org/14178013

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@14371 ce2b1a6d-e550-0410-aec6-3dcde31c8c00