If the input to an HChange is of type smi, then no need to mark gvn flag changes new space promotion.

BUG=

Review URL: https://codereview.chromium.org/14253010

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@14401 ce2b1a6d-e550-0410-aec6-3dcde31c8c00