Add a new cpu variant named kabylake

This is needed to perform instruction simplification
on cpus that support AVX2 feature flag.

Test: ./test.py --host --64, test-art-host-gtest
Change-Id: I3e300dff56b8ec5d6f170f3c3840faafa87c3dd6
Signed-off-by: Shalini Salomi Bodapati <shalini.salomi.bodapati@intel.com>