[Target/ARM] Remove unused private

[davide]

Summary

I'm trying to port this pass to AArch64 and noticed this.

[rengolin]

Ouch. LGTM. Thanks!

llvm/trunk/lib/Target/ARM/ARMOptimizeBarriersPass.cpp

public:
   static char ID;
   ARMOptimizeBarriersPass() : MachineFunctionPass(ID) {}
 
   bool runOnMachineFunction(MachineFunction &Fn) override;
 
   const char *getPassName() const override {
     return "optimise barriers pass";
   }
-
-private:
 };
 char ARMOptimizeBarriersPass::ID = 0;
 }
 
 // Returns whether the instruction can safely move past a DMB instruction
 // The current implementation allows this iif MI does not have any possible
 // memory access
 static bool CanMovePastDMB(const MachineInstr *MI) {