lavfi/dnn_backend_openvino.c: Fix Memory Leak for RequestItem

Fix memory leak for RequestItem upon error while pushing to the
request_queue in the completion callback.

Signed-off-by: Shubhanshu Saxena <shubhanshu.e01@gmail.com>

libavfilter/dnn/dnn_backend_openvino.c

@@ -293,6 +293,8 @@ static void infer_completion_callback(void *args)
 
     request->inference_count = 0;
     if (ff_safe_queue_push_back(requestq, request) < 0) {
+        ie_infer_request_free(&request->infer_request);
+        av_freep(&request);
         av_log(ctx, AV_LOG_ERROR, "Failed to push back request_queue.\n");
         return;
     }