Fix Qwen2AudioForConditionalGeneration.forward() and test_flash_attn_kernels_inference_equivalence (#39503)

* Add missing cache_position argument.

* Pass cache_position to language model.

* Overwrite prepare_inputs_for_generation.

* Set model to half precision for Flash Attention test.

* Cast model to bfloat16.

tests/models/qwen2_audio/test_modeling_qwen2_audio.py

@@ -34,6 +34,7 @@ from transformers.testing_utils import (
     torch_device,
 )
 
+from ...generation.test_utils import GenerationTesterMixin
 from ...test_configuration_common import ConfigTester
 from ...test_modeling_common import ModelTesterMixin, floats_tensor, ids_tensor
 
@@ -132,14 +133,12 @@ class Qwen2AudioModelTester:
 
 
 @require_torch
-class Qwen2AudioForConditionalGenerationModelTest(ModelTesterMixin, unittest.TestCase):
+class Qwen2AudioForConditionalGenerationModelTest(ModelTesterMixin, GenerationTesterMixin, unittest.TestCase):
     """
     Model tester for `Qwen2AudioForConditionalGeneration`.
     """
 
     all_model_classes = (Qwen2AudioForConditionalGeneration,) if is_torch_available() else ()
-    # Doesn't run generation tests. TODO eustache/joao: some generation tests are broken, the errors seem cache-related
-    all_generative_model_classes = ()
     test_pruning = False
     test_head_masking = False
     _is_composite = True