This matches the declaration with official documentation and fixes the following two compiler errors in apitrace project.
d3d9trace.cpp:28469:59: error: invalid conversion from 'const DXVA2_ConfigPictureDecode*' to 'DXVA2_ConfigPictureDecode*' [-fpermissive] d3d9trace.cpp:28194:65: error: invalid conversion from 'void*' to 'IUnknown*' [-fpermissive]
-- v2: include: Fix IDirectXVideoDecoderService declaration in dxva2api.idl.