avutil/hwcontext_d3d11va: fix type arguments passed to IDXGIAdapter2_GetDesc()

libavutil/hwcontext_d3d11va.c: In function 'd3d11va_device_create':
libavutil/hwcontext_d3d11va.c:554:46: warning: passing argument 2 of 'pAdapter->lpVtbl->GetDesc' from incompatible pointer type [-Wincompatible-pointer-types]
         hr = IDXGIAdapter2_GetDesc(pAdapter, &desc);
                                              ^
libavutil/hwcontext_d3d11va.c:554:46: note: expected 'DXGI_ADAPTER_DESC * {aka struct DXGI_ADAPTER_DESC *}' but argument is of type 'DXGI_ADAPTER_DESC2 * {aka struct DXGI_ADAPTER_DESC2 *}'

Reviewed-by: Jean-Baptiste Kempf <jb@videolan.org>
Signed-off-by: James Almer <jamrial@gmail.com>