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/Support/YAMLParser.cpp b/llvm/lib/Support/YAMLParser.cpp
index d55da5e..5ca28a0 100644
--- a/llvm/lib/Support/YAMLParser.cpp
+++ b/llvm/lib/Support/YAMLParser.cpp
@@ -144,8 +144,8 @@
 
   Token() : Kind(TK_Error) {}
 };
-}
-}
+} // namespace yaml
+} // namespace llvm
 
 namespace llvm {
 template<>
@@ -178,7 +178,7 @@
 
   BumpPtrAllocator Alloc;
 };
-}
+} // namespace llvm
 
 typedef ilist<Token> TokenQueueT;
 
@@ -203,7 +203,7 @@
     return Tok == Other.Tok;
   }
 };
-}
+} // namespace
 
 /// @brief The Unicode scalar value of a UTF-8 minimal well-formed code unit
 ///        subsequence and the subsequence's length in code units (uint8_t).