[ARM] Add Kryo to available targets

Summary:
Host CPU detection now supports Kryo, so we need to recognize it in ARM
target.

Reviewers: mcrosier, t.p.northover, rengolin, echristo, srhines

Reviewed By: t.p.northover, echristo

Subscribers: aemerson

Differential Revision: https://reviews.llvm.org/D31775

llvm-svn: 299674