[ARM64] Ports the Cortex-A53 Machine Model description from AArch64.

Summary:
This port includes the rudimentary latencies that were provided for
the Cortex-A53 Machine Model in the AArch64 backend. It also changes
the SchedAlias for COPY in the Cyclone model to an explicit
WriteRes mapping to avoid conflicts in other subtargets.

Differential Revision: http://reviews.llvm.org/D3427
Patch by Dave Estes <cestes@codeaurora.org>!