Fixed/added namespace ending comments using clang-tidy. NFC

The patch is generated using this command:

tools/clang/tools/extra/clang-tidy/tool/run-clang-tidy.py -fix \
  -checks=-*,llvm-namespace-comment -header-filter='llvm/.*|clang/.*' \
  llvm/lib/


Thanks to Eugene Kosov for the original patch!

llvm-svn: 240137

llvm/lib/CodeGen/MachineCopyPropagation.cpp

@@ -55,7 +55,7 @@ namespace {
                                  DenseMap<unsigned, MachineInstr*> &AvailCopyMap);
     bool CopyPropagateBlock(MachineBasicBlock &MBB);
   };
-}
+} // namespace
 char MachineCopyPropagation::ID = 0;
 char &llvm::MachineCopyPropagationID = MachineCopyPropagation::ID;