[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

llvm/lib/Target/RISCV/MCTargetDesc/RISCVBaseInfo.cpp

@@ -182,9 +182,4 @@ void RISCVVType::printVType(unsigned VType, raw_ostream &OS) {
     OS << ", mu";
 }
 
-bool isFaultFirstLoad(const MachineInstr &MI) {
-  return MI.getNumExplicitDefs() == 2 && MI.modifiesRegister(RISCV::VL) &&
-         !MI.isInlineAsm();
-}
-
 } // namespace llvm

llvm/lib/Target/RISCV/MCTargetDesc/RISCVBaseInfo.h

@@ -433,7 +433,13 @@ void printVType(unsigned VType, raw_ostream &OS);
 
 } // namespace RISCVVType
 
-bool isFaultFirstLoad(const MachineInstr &MI);
+namespace RISCVVInstInfo {
+inline static bool isFaultFirstLoad(const MachineInstr &MI) {
+  return MI.getNumExplicitDefs() == 2 && MI.modifiesRegister(RISCV::VL) &&
+         !MI.isInlineAsm();
+}
+} // namespace RISCVVInstInfo
+
 } // namespace llvm
 
 #endif

llvm/lib/Target/RISCV/RISCVInsertVSETVLI.cpp

@@ -1414,7 +1414,7 @@ void RISCVInsertVSETVLI::doLocalPostpass(MachineBasicBlock &MBB) {
 void RISCVInsertVSETVLI::insertReadVL(MachineBasicBlock &MBB) {
   for (auto I = MBB.begin(), E = MBB.end(); I != E;) {
     MachineInstr &MI = *I++;
-    if (isFaultFirstLoad(MI)) {
+    if (RISCVVInstInfo::isFaultFirstLoad(MI)) {
       Register VLOutput = MI.getOperand(1).getReg();
       if (!MRI->use_nodbg_empty(VLOutput))
         BuildMI(MBB, I, MI.getDebugLoc(), TII->get(RISCV::PseudoReadVL),

llvm/lib/Target/RISCV/RISCVMCInstLower.cpp

@@ -158,7 +158,7 @@ static bool lowerRISCVVMachineInstrToMCInst(const MachineInstr *MI,
   if (RISCVII::hasSEWOp(TSFlags))
     --NumOps;
 
-  bool hasVLOutput = isFaultFirstLoad(*MI);
+  bool hasVLOutput = RISCVVInstInfo::isFaultFirstLoad(*MI);
   for (unsigned OpNo = 0; OpNo != NumOps; ++OpNo) {
     const MachineOperand &MO = MI->getOperand(OpNo);
     // Skip vl ouput. It should be the second output.