[llvm] [ARM] FIX: change `pkhtb` custom parsing produce NoMatch rather than Error (PR #85765)

[Alfie Richards via llvm-commits]

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@@ -4318,6 +4318,23 @@ int ARMAsmParser::tryParseShiftRegister(OperandVector &Operands) {
     }
   }
 
+  auto MnemonicOp = static_cast<ARMOperand &>(*Operands[0]);
+  // These instructions handle shift operands as seperate operators to the
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AlfieRichardsArm wrote:

Done

https://github.com/llvm/llvm-project/pull/85765