[clang] [mlir] [OpenACC][NFCI] Implement 'helpers' for all of the clauses I've used so far (PR #137396)

[Andy Kaylor via cfe-commits]

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@@ -1535,6 +1560,21 @@ def OpenACC_SerialOp : OpenACC_Op<"serial",
     static mlir::acc::Construct getConstructId() {
       return mlir::acc::Construct::acc_construct_serial;
     }
+    /// Add an entry to the 'async-only' attribute (clause spelled without
+    /// arguments)for each of the additional device types (or a none if it is
+    /// empty).
+    void addAsyncOnly(MLIRContext *, llvm::ArrayRef<DeviceType>);
+    /// Add a value to the 'async' with the current list of device types.
+    void addAsyncOperand(MLIRContext *, mlir::Value,
+                         llvm::ArrayRef<DeviceType>);
+    /// Add an entry to the 'wait-only' attribute (clause spelled without
+    /// arguments)for each of the additional device types (or a none if it is
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andykaylor wrote:

```suggestion
    /// arguments) for each of the additional device types (or a none if it is
```

https://github.com/llvm/llvm-project/pull/137396