dxva2: Add ifdefs around structs that might not be available

Signed-off-by: Martin Storsjö <martin@martin.st>

libavcodec/dxva2.c

@@ -132,8 +132,12 @@ int ff_dxva2_common_end_frame(AVCodecContext *avctx, AVFrame *frame,
 {
     AVDXVAContext *ctx = avctx->hwaccel_context;
     unsigned               buffer_count = 0;
+#if CONFIG_D3D11VA
     D3D11_VIDEO_DECODER_BUFFER_DESC buffer11[4];
+#endif
+#if CONFIG_DXVA2
     DXVA2_DecodeBufferDesc          buffer2[4];
+#endif
     DECODER_BUFFER_DESC             *buffer,*buffer_slice;
     int result, runs = 0;
     HRESULT hr;