Remove --prof-auto flag

There is already --prof-lazy flag which should be enough.

BUG=None
R=yangguo@chromium.org

Review URL: https://codereview.chromium.org/20482003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@15909 ce2b1a6d-e550-0410-aec6-3dcde31c8c00