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/UnreachableBlockElim.cpp b/llvm/lib/CodeGen/UnreachableBlockElim.cpp
index d393e10..5c54cdb 100644
--- a/llvm/lib/CodeGen/UnreachableBlockElim.cpp
+++ b/llvm/lib/CodeGen/UnreachableBlockElim.cpp
@@ -51,7 +51,7 @@
       AU.addPreserved<DominatorTreeWrapperPass>();
     }
   };
-}
+} // namespace
 char UnreachableBlockElim::ID = 0;
 INITIALIZE_PASS(UnreachableBlockElim, "unreachableblockelim",
                 "Remove unreachable blocks from the CFG", false, false)