[llvm] [AMDGPU][MC] GFX9 - allow op_sel in v_interp_p2_f16 (PR #150712)

[Matt Arsenault via llvm-commits]

================
@@ -9310,6 +9310,38 @@ void AMDGPUAsmParser::cvtVOP3Interp(MCInst &Inst, const OperandVector &Operands)
   if (AMDGPU::hasNamedOperand(Opc, AMDGPU::OpName::omod))
     addOptionalImmOperand(Inst, Operands, OptionalIdx,
                           AMDGPUOperand::ImmTyOModSI);
+
+  // Some v_interp instrutions use op_sel[3] for dst.
----------------
arsenm wrote:

```suggestion
  // Some v_interp instructions use op_sel[3] for dst.
```

https://github.com/llvm/llvm-project/pull/150712