[AArch64] Basic Sched Model for Cortex-A57.
Patch by Dave Estes<cestes@codeaurora.org>
Differential Revision: http://reviews.llvm.org/D4008

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210705 91177308-0d34-0410-b5e6-96231b3b80d8