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/RegAllocFast.cpp b/llvm/lib/CodeGen/RegAllocFast.cpp
index fd3d4d7..4a46638 100644
--- a/llvm/lib/CodeGen/RegAllocFast.cpp
+++ b/llvm/lib/CodeGen/RegAllocFast.cpp
@@ -194,7 +194,7 @@
     bool setPhysReg(MachineInstr *MI, unsigned OpNum, unsigned PhysReg);
   };
   char RAFast::ID = 0;
-}
+} // namespace
 
 /// getStackSpaceFor - This allocates space for the specified virtual register
 /// to be held on the stack.