[3.0] direct3d11: only send the HDR metadata when they change

Newer Windows issue this warning if we send metadata with each picture:

DXGI WARNING: IDXGISwapChain4::SetHDRMetaData: Redundant invocation on unchanged metadata could result in presentation performance inefficiency. [ MISCELLANEOUS WARNING #295 (closed): ]

Similar code as done in 26954081 for VLC 4.0.