AMDGPU: Stop forcing RequiresCodeGenSCCOrder (#169522)

This hasn't been strictly necessary since c897c13.
Practically this makes little difference; we still enable IPRA
by default which implies this option. By removing this explicit
force, -enable-ipra=0 has the expected change in the pass pipeline
to remove the DummyCGSCC runs.

Author: arsenm

llvm/lib/Target/AMDGPU/AMDGPUTargetMachine.cpp

@@ -1226,10 +1226,6 @@ class GCNPassConfig final : public AMDGPUPassConfig {
 public:
   GCNPassConfig(TargetMachine &TM, PassManagerBase &PM)
       : AMDGPUPassConfig(TM, PM) {
-    // It is necessary to know the register usage of the entire call graph.  We
-    // allow calls without EnableAMDGPUFunctionCalls if they are marked
-    // noinline, so this is always required.
-    setRequiresCodeGenSCCOrder(true);
     substitutePass(&PostRASchedulerID, &PostMachineSchedulerID);
   }