Revert "Refactor ARM subarchitecture parsing"

This reverts commit 7b4a6882467e7fef4516a0cbc418cbfce0fc6f6d.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@212521 91177308-0d34-0410-b5e6-96231b3b80d8