ARM64: remove currently trivial switch statement

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@205167 91177308-0d34-0410-b5e6-96231b3b80d8
Remove unused variable


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@205169 91177308-0d34-0410-b5e6-96231b3b80d8