[NFC][LLVM] Code cleanup in InstructionNamer.cpp (#162689)

Make file local function static and use explicit type for Arg.

Author: jurahul

llvm/lib/Transforms/Utils/InstructionNamer.cpp

@@ -20,9 +20,8 @@
 
 using namespace llvm;
 
-namespace {
-void nameInstructions(Function &F) {
-  for (auto &Arg : F.args()) {
+static void nameInstructions(Function &F) {
+  for (Argument &Arg : F.args()) {
     if (!Arg.hasName())
       Arg.setName("arg");
   }
@@ -38,8 +37,6 @@ void nameInstructions(Function &F) {
   }
 }
 
-} // namespace
-
 PreservedAnalyses InstructionNamerPass::run(Function &F,
                                             FunctionAnalysisManager &FAM) {
   nameInstructions(F);