[RISCV] move `isFaultFirstLoad` into `RISCVInstrInfo`

Fix build errors in D126794

```
ld.lld: error: undefined symbol: llvm::MachineInstr::getNumExplicitDefs() const
>>> referenced by RISCVBaseInfo.cpp
>>>               RISCVBaseInfo.cpp.o:(llvm::isFaultFirstLoad(llvm::MachineInstr const&)) in archive lib/libLLVMRISCVDesc.a

ld.lld: error: undefined symbol: llvm::MachineInstr::findRegisterDefOperandIdx(llvm::Register, bool, bool, llvm::TargetRegisterInfo const*) const
>>> referenced by RISCVBaseInfo.cpp
>>>               RISCVBaseInfo.cpp.o:(llvm::isFaultFirstLoad(llvm::MachineInstr const&)) in archive lib/libLLVMRISCVDesc.a
clang-15: error: linker command failed with exit code 1 (use -v to see invocation)
```

Reviewed By: fakepaper56

Differential Revision: https://reviews.llvm.org/D127477