[ARM64] Adds Cortex-A53 scheduling support for vector load/store post.
Patch by Dave Estes<cestes@codeaurora.org>!
PR19761 http://reviews.llvm.org/D3829

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209176 91177308-0d34-0410-b5e6-96231b3b80d8