[AArch64] Enabled AA support for Cortex-A53.

Patch by Sanjin Sijaric <ssijaric@codeaurora.org>!
Phabricator Review: http://reviews.llvm.org/D5103

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@217370 91177308-0d34-0410-b5e6-96231b3b80d8