Construct the MCStreamer before constructing the MCTargetStreamer.

This has a few advantages:
* Only targets that use a MCTargetStreamer have to worry about it.
* There is never a MCTargetStreamer without a MCStreamer, so we can use a
  reference.
* A MCTargetStreamer can talk to the MCStreamer in its constructor.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@200129 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/R600/MCTargetDesc/AMDGPUMCTargetDesc.cpp

@@ -88,7 +88,7 @@ static MCStreamer *createMCStreamer(const Target &T, StringRef TT,
                                     MCCodeEmitter *_Emitter,
                                     bool RelaxAll,
                                     bool NoExecStack) {
-  return createELFStreamer(Ctx, 0, MAB, _OS, _Emitter, false, false);
+  return createELFStreamer(Ctx, MAB, _OS, _Emitter, false, false);
 }
 
 extern "C" void LLVMInitializeR600TargetMC() {