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
diff --git a/llvm/lib/CodeGen/MachineCombiner.cpp b/llvm/lib/CodeGen/MachineCombiner.cpp
index 39adce3..cc9b1be 100644
--- a/llvm/lib/CodeGen/MachineCombiner.cpp
+++ b/llvm/lib/CodeGen/MachineCombiner.cpp
@@ -78,7 +78,7 @@
   void instr2instrSC(SmallVectorImpl<MachineInstr *> &Instrs,
                      SmallVectorImpl<const MCSchedClassDesc *> &InstrsSC);
 };
-}
+} // namespace
 
 char MachineCombiner::ID = 0;
 char &llvm::MachineCombinerID = MachineCombiner::ID;