ffmpeg_dxva2: call GetDesktopWindow() in place of GetShellWindow()

This fixes compilation with latest MinGW, it does not seem to affect
MSYS2/MinGW-64.

ffmpeg_dxva2.c

@@ -364,7 +364,7 @@ static int dxva2_alloc(AVCodecContext *s)
     d3dpp.SwapEffect       = D3DSWAPEFFECT_DISCARD;
     d3dpp.Flags            = D3DPRESENTFLAG_VIDEO;
 
-    hr = IDirect3D9_CreateDevice(ctx->d3d9, adapter, D3DDEVTYPE_HAL, GetShellWindow(),
+    hr = IDirect3D9_CreateDevice(ctx->d3d9, adapter, D3DDEVTYPE_HAL, GetDesktopWindow(),
                                  D3DCREATE_SOFTWARE_VERTEXPROCESSING | D3DCREATE_MULTITHREADED | D3DCREATE_FPU_PRESERVE,
                                  &d3dpp, &ctx->d3d9device);
     if (FAILED(hr)) {