[RISCV] Remove Match_InvalidXSfmmVType. NFC (#168465)

It's not reachable because the custom parser will accept or fail the
whole instruction.

Author: topperc

llvm/lib/Target/RISCV/AsmParser/RISCVAsmParser.cpp

@@ -1654,10 +1654,6 @@ bool RISCVAsmParser::matchAndEmitInstruction(SMLoc IDLoc, unsigned &Opcode,
     return generateImmOutOfRangeError(
         Operands, ErrorInfo, -1, (1 << 5) - 1,
         "immediate must be non-zero in the range");
-  case Match_InvalidXSfmmVType: {
-    SMLoc ErrorLoc = ((RISCVOperand &)*Operands[ErrorInfo]).getStartLoc();
-    return generateXSfmmVTypeError(ErrorLoc);
-  }
   case Match_InvalidVTypeI: {
     SMLoc ErrorLoc = ((RISCVOperand &)*Operands[ErrorInfo]).getStartLoc();
     return generateVTypeError(ErrorLoc);

llvm/lib/Target/RISCV/RISCVInstrInfoXSfmm.td

@@ -13,7 +13,6 @@
 def XSfmmVTypeAsmOperand : AsmOperandClass {
   let Name = "XSfmmVType";
   let ParserMethod = "parseXSfmmVType";
-  let DiagnosticType = "InvalidXSfmmVType";
   let RenderMethod = "addVTypeIOperands";
 }