[RISCV] Remove unnecessary initialization from RISCVPostRAExpandPseudo pass constructor.

It is already initialized in RISCVTargetMachine.cpp

Author: topperc

llvm/lib/Target/RISCV/RISCVPostRAExpandPseudoInsts.cpp

@@ -31,9 +31,7 @@ class RISCVPostRAExpandPseudo : public MachineFunctionPass {
   const RISCVInstrInfo *TII;
   static char ID;
 
-  RISCVPostRAExpandPseudo() : MachineFunctionPass(ID) {
-    initializeRISCVPostRAExpandPseudoPass(*PassRegistry::getPassRegistry());
-  }
+  RISCVPostRAExpandPseudo() : MachineFunctionPass(ID) {}
 
   bool runOnMachineFunction(MachineFunction &MF) override;