Split the object streamer callback in one per file format.

There are two main advantages to doing this

* Targets that only need to handle one of the formats specially don't have
  to worry about the others. For example, x86 now only registers a
  constructor for the COFF streamer.

* Changes to the arguments passed to one format constructor will not impact
  the other formats.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@232699 91177308-0d34-0410-b5e6-96231b3b80d8

lib/MC/MCObjectStreamer.cpp

@@ -423,16 +423,3 @@ void MCObjectStreamer::FinishImpl() {
   flushPendingLabels(nullptr);
   getAssembler().Finish();
 }
-
-MCStreamer *llvm::createObjectStreamer(const Triple &T, MCContext &Ctx,
-                                       MCAsmBackend &TAB, raw_ostream &OS,
-                                       MCCodeEmitter *Emitter,
-                                       const MCSubtargetInfo &STI,
-                                       bool RelaxAll) {
-  switch (T.getObjectFormat()) {
-  default:
-    return nullptr;
-  case Triple::ELF:
-    return createELFStreamer(Ctx, TAB, OS, Emitter, RelaxAll);
-  }
-}