Update docs: Add warning for device_map=None for load_checkpoint_and_…

…dispatch (#2308)

* Update docs: Add warning for device_map=None for load_checkpoint_and_dispatch

* Fix style errors.

src/accelerate/big_modeling.py

@@ -73,6 +73,8 @@ def init_empty_weights(include_buffers: bool = None):
 
     Any model created under this context manager has no weights. As such you can't do something like
     `model.to(some_device)` with it. To load weights inside your empty model, see [`load_checkpoint_and_dispatch`].
+    Make sure to overwrite the default device_map param for [`load_checkpoint_and_dispatch`], otherwise dispatch is not
+    called.
 
     </Tip>
     """
@@ -479,7 +481,8 @@ def load_checkpoint_and_dispatch(
             name, once a given module name is inside, every submodule of it will be sent to the same device.
 
             To have Accelerate compute the most optimized `device_map` automatically, set `device_map="auto"`. For more
-            information about each option see [here](big_modeling#designing-a-device-map).
+            information about each option see [here](../concept_guides/big_model_inference#designing-a-device-map).
+            Defaults to None, which means [`dispatch_model`] will not be called.
         max_memory (`Dict`, *optional*):
             A dictionary device identifier to maximum memory. Will default to the maximum memory available for each GPU
             and the available CPU RAM if unset.