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/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index 566c9a0..0eff930 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -6134,7 +6134,7 @@
     : SelectionDAG::DAGUpdateListener(d), UI(ui), UE(ue) {}
 };
 
-}
+} // namespace
 
 /// ReplaceAllUsesWith - Modify anything using 'From' to use 'To' instead.
 /// This can cause recursive merging of nodes in the DAG.
@@ -6344,7 +6344,7 @@
   bool operator<(const UseMemo &L, const UseMemo &R) {
     return (intptr_t)L.User < (intptr_t)R.User;
   }
-}
+} // namespace
 
 /// ReplaceAllUsesOfValuesWith - Replace any uses of From with To, leaving
 /// uses of other values produced by From.getNode() alone.  The same value
@@ -6589,7 +6589,7 @@
         VTs.push_back(MVT((MVT::SimpleValueType)i));
     }
   };
-}
+} // namespace
 
 static ManagedStatic<std::set<EVT, EVT::compareRawBits> > EVTs;
 static ManagedStatic<EVTArray> SimpleVTArray;