ARM: add cyclone CPU with ZeroCycleZeroing feature.

The Cyclone CPU is similar to swift for most LLVM purposes, but does have two
preferred instructions for zeroing a VFP register. This teaches LLVM about
them.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@205309 91177308-0d34-0410-b5e6-96231b3b80d8