vf_hwupload_cuda: Fix build error

Broken by e3fb74f7.
Signed-off-by: NDiego Biurrun <diego@biurrun.de>

libavfilter/vf_hwupload_cuda.c

@@ -151,7 +151,7 @@ static int cudaupload_config_output(AVFilterLink *outlink)
 static int cudaupload_filter_frame(AVFilterLink *link, AVFrame *in)
 {
     AVFilterContext   *ctx = link->dst;
-    CudaUploadContext   *s = ctx->priv;
+    AVFilterLink  *outlink = ctx->outputs[0];
 
     AVFrame *out = NULL;
     int ret;