ARM MC: sort source files in CMakeLists

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@205832 91177308-0d34-0410-b5e6-96231b3b80d8
ARM MC: 80 column

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@205833 91177308-0d34-0410-b5e6-96231b3b80d8