[turbofan] re-enable some tests for arm64.

Those tests were disabled because of an issue in TruncateDoubleToI which has
been fixed since.

BUG=
R=bmeurer@chromium.org

Review URL: https://codereview.chromium.org/605253002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24371 ce2b1a6d-e550-0410-aec6-3dcde31c8c00