Update local import for ppl (#11866)

Co-authored-by: jenniew <jenniewang123@gmail.com>

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

@@ -21,7 +21,6 @@ import argparse
 import torch
 from tqdm import tqdm
 from datasets import load_dataset
-from ipex_llm.utils.common import invalidInputError
 
 
 parser = argparse.ArgumentParser()
@@ -63,6 +62,7 @@ elif args.data_path:
         data = f.read()
     encodings = tokenizer(data.decode("utf-8").strip("\n"), return_tensors="pt")
 else:
+    from ipex_llm.utils.common import invalidInputError
     raise invalidInputError(False, "Must specify either dataset or datapath.")
 
 if not args.max_length: