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/Transforms/IPO/DeadArgumentElimination.cpp b/llvm/lib/Transforms/IPO/DeadArgumentElimination.cpp
index 76898f2..6bfd3d1 100644
--- a/llvm/lib/Transforms/IPO/DeadArgumentElimination.cpp
+++ b/llvm/lib/Transforms/IPO/DeadArgumentElimination.cpp
@@ -159,7 +159,7 @@
     bool DeleteDeadVarargs(Function &Fn);
     bool RemoveDeadArgumentsFromCallers(Function &Fn);
   };
-}
+} // namespace
 
 
 char DAE::ID = 0;
@@ -175,7 +175,7 @@
 
     bool ShouldHackArguments() const override { return true; }
   };
-}
+} // namespace
 
 char DAH::ID = 0;
 INITIALIZE_PASS(DAH, "deadarghaX0r",