fix ppl (#10996)

python/llm/dev/benchmark/perplexity/ppl.py

@@ -74,6 +74,7 @@ class BigDLPPL:
 
             ppl_mean = np.mean(np.array(ppls)[~np.isnan(np.array(ppls))])
         finally:
+            if self.device == "xpu":
                 torch.xpu.synchronize()
                 torch.xpu.empty_cache()
             del self.model

python/llm/dev/benchmark/perplexity/run.py

@@ -100,7 +100,7 @@ def main():
         dumped = json.dumps(results, indent=2)
         print(dumped)
 
-        if args.output_path:
+        if output_path:
             with open(f"{log_dir}/result.json", "w") as f:
                 f.write(dumped)