Add subtarget feature support for Cortex-A53

Some previous implicit defaults have changed, for example FP and NEON
are now on by default.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@192590 91177308-0d34-0410-b5e6-96231b3b80d8
Add Cortex-A57 support

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@192591 91177308-0d34-0410-b5e6-96231b3b80d8