[RISCV] Remove BREV8 and ORC_B from hasAllNBitUsers in RISCVOptWInstrs. (#147830)

These instructions operate on bytes so we need to round the demanded
bits up to the nearest byte which we aren't doing. I think we forgot to
update this when we changed from hasAllWUsers to hasNBitUsers.

We don't have any test case for these instruction so remove them until
we can put together a test.

llvm/lib/Target/RISCV/RISCVOptWInstrs.cpp

@@ -311,9 +311,7 @@ static bool hasAllNBitUsers(const MachineInstr &OrigMI,
       case RISCV::XORI:
 
       case RISCV::ANDN:
-      case RISCV::BREV8:
       case RISCV::CLMUL:
-      case RISCV::ORC_B:
       case RISCV::ORN:
       case RISCV::SH1ADD:
       case RISCV::SH2ADD: