[TODO] DAC functionality not implemented

[smdn]

The interface is not definite.

Smdn.Devices.MCP2221/src/Smdn.Devices.MCP2221/Smdn.Devices.MCP2221/MCP2221.GPs.DAC.cs

Lines 10 to 20 in 1931ceb

	internal interface IDACFunctionality {
	ValueTask ConfigureAsDACAsync(
	CancellationToken cancellationToken = default
	);
	void ConfigureAsDAC(
	CancellationToken cancellationToken = default
	);
	#if __FUTURE_VERSION
	int DACValue { set; }
	#endif
	}