LLM: fix mpt load_low_bit issue (#10075)

* fix

* retry

* retry

python/llm/src/bigdl/llm/transformers/model.py

@@ -361,6 +361,10 @@ class _BaseAutoModelClass:
                                      cpu_embedding=cpu_embedding, lightweight_bmm=lightweight_bmm,
                                      torch_dtype=kwargs.get("torch_dtype", 'auto'))
         model.config.update({"bigdl_transformers_low_bit": q_k})
+
+        # enable tie_word_embeddings for MPT
+        # refer to https://huggingface.co/mosaicml/mpt-7b-chat/blob/main/modeling_mpt.py#L232
+        if model.config.architectures[0] != 'MPTForCausalLM':
             model.config.update({"tie_word_embeddings": False})
 
         # add save_low_bit to pretrained model dynamically