Move testcase to the appropriate X86 subdirectory.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@197701 91177308-0d34-0410-b5e6-96231b3b80d8
Revert r197682, "[CMake] Introduce LIT in add_lit_target."

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@197703 91177308-0d34-0410-b5e6-96231b3b80d8