ARM64: Fix native cctest

CPUFeatures::Probe has been modified such that it can be called only once, but
the cctests make two calls in native builds: once in VM init, and once in each
test setup. This patch removes the call in the test setup.

BUG=
R=ulan@chromium.org

Review URL: https://codereview.chromium.org/285273003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@21337 ce2b1a6d-e550-0410-aec6-3dcde31c8c00