Reland "[NFC][AMDGPU] Do not flush after printing every instruction (#95237)"

It's very expensive and doesn't achieve anything.

I one test I did, it saves almost 10s on a 2m23s build, bringing it down
to 2m15s using a downstream branch.

Author: Pierre-vh

llvm/lib/Target/AMDGPU/MCTargetDesc/AMDGPUInstPrinter.cpp

@@ -43,7 +43,6 @@ void AMDGPUInstPrinter::printRegName(raw_ostream &OS, MCRegister Reg) const {
 void AMDGPUInstPrinter::printInst(const MCInst *MI, uint64_t Address,
                                   StringRef Annot, const MCSubtargetInfo &STI,
                                   raw_ostream &OS) {
-  OS.flush();
   printInstruction(MI, Address, STI, OS);
   printAnnotation(OS, Annot);
 }

llvm/lib/Target/AMDGPU/MCTargetDesc/R600InstPrinter.cpp

@@ -21,7 +21,6 @@ using namespace llvm;
 void R600InstPrinter::printInst(const MCInst *MI, uint64_t Address,
                                 StringRef Annot, const MCSubtargetInfo &STI,
                                 raw_ostream &O) {
-  O.flush();
   printInstruction(MI, Address, O);
   printAnnotation(O, Annot);
 }