[llvm] [VPlan] Separate out logic to manage IR flags to VPIRFlags (NFC). (PR #140621)

[via llvm-commits]

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@@ -164,25 +164,19 @@ class VPBuilder {
                               DebugLoc DL, const Twine &Name = "") {
     return createInstruction(Opcode, Operands, DL, Name);
   }
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ayalz wrote:

nit, also above between lines 162,163
```suggestion
  }

```

https://github.com/llvm/llvm-project/pull/140621