[NFC][NVPTX] Remove dead comment and commented code

A confusing comment after the last return statement in
`NVPTXAsmPrinter::doFinalization` referred to a preprocessor macro
(NVISA) that has never existed since the NVPTX backend has been a part
of upstream llvm - as far as the pickaxe will tell me anyway. Thus I've
removed it.

Differential Revision: https://reviews.llvm.org/D140399

llvm/lib/Target/NVPTX/NVPTXAsmPrinter.cpp

@@ -913,15 +913,6 @@ bool NVPTXAsmPrinter::doFinalization(Module &M) {
   TS->outputDwarfFileDirectives();
 
   return ret;
-
-  //bool Result = AsmPrinter::doFinalization(M);
-  // Instead of calling the parents doFinalization, we may
-  // clone parents doFinalization and customize here.
-  // Currently, we if NVISA out the EmitGlobals() in
-  // parent's doFinalization, which is too intrusive.
-  //
-  // Same for the doInitialization.
-  //return Result;
 }
 
 // This function emits appropriate linkage directives for