add missing GenerationConfig

Author: rnwang04

tools/llm_bench/task/text_generation.py

@@ -315,6 +315,7 @@ def run_text_generation_genai(input_text, num, model, tokenizer, args, iter_data
         if args['infer_count'] is not None:
             out_str += 'all max_output_token_size: {} * {}'.format(args['infer_count'], args['batch_size'])
         log.info(out_str)
+    from openvino_genai import GenerationConfig
     gen_config = model.get_generation_config() if hasattr(model, 'get_generation_config') else GenerationConfig()
     gen_config.max_new_tokens = max_gen_tokens
     # llama-3-8b-instruct's generation_config.json has 4096 max_length.