[RISCV] Fix -Wunused-function in RISCVVLOptimizer.cpp (NFC)
/llvm-project/llvm/lib/Target/RISCV/RISCVVLOptimizer.cpp:125:21:
error: unused function 'operator<<' [-Werror,-Wunused-function]
static raw_ostream &operator<<(raw_ostream &OS, const OperandInfo &OI) {
^
1 error generated.
llvm-project
8b179162 - [RISCV] Fix -Wunused-function in RISCVVLOptimizer.cpp (NFC)
