[Mixtral & Mistral] Add support for sdpa (#28133)

* some nits

* update test

* add support d\sd[a

* remove some dummy inputs

* all good

* style

* nits

* fixes

* fix more copies

* nits

* styling

* fix

* Update src/transformers/models/mistral/modeling_mistral.py

Co-authored-by: Younes Belkada <49240599+younesbelkada@users.noreply.github.com>

* add a slow test just to be sure

* fixup

---------

Co-authored-by: Younes Belkada <49240599+younesbelkada@users.noreply.github.com>

tests/models/mixtral/test_modeling_mixtral.py

@@ -38,11 +38,7 @@ from ...test_pipeline_mixin import PipelineTesterMixin
 if is_torch_available():
     import torch
 
-    from transformers import (
-        MixtralForCausalLM,
-        MixtralForSequenceClassification,
-        MixtralModel,
-    )
+    from transformers import MixtralForCausalLM, MixtralForSequenceClassification, MixtralModel
 
 
 class MixtralModelTester: