[ARM64] Increases the Sched Model accuracy for Cortex-A53.
Patch by Dave Estes <cestes@codeaurora.org>
http://reviews.llvm.org/D3769

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209001 91177308-0d34-0410-b5e6-96231b3b80d8