[NFC][RISCV] Simplify pass arg of RISCVMergeBaseOffsetOpt

llvm/lib/Target/RISCV/RISCVMergeBaseOffset.cpp

 
 private:
   MachineRegisterInfo *MRI;
   std::set<MachineInstr *> DeadInstrs;
 };
 } // end anonymous namespace
 
 char RISCVMergeBaseOffsetOpt::ID = 0;
-INITIALIZE_PASS(RISCVMergeBaseOffsetOpt, "riscv-merge-base-offset",
+INITIALIZE_PASS(RISCVMergeBaseOffsetOpt, DEBUG_TYPE,
                 RISCV_MERGE_BASE_OFFSET_NAME, false, false)
 
 // Detect the pattern:
 //   lui   vreg1, %hi(s)
 //   addi  vreg2, vreg1, %lo(s)
 //
 //   Pattern only accepted if:
 //     1) ADDI has only one use.