rework inputs preparation for OVModelForCausalLM

[eaidova]

What does this PR do?

Fixes # (issue)

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• This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
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[eaidova]

@echarlaix looks like phi model used in tests was removed from hub
FAILED tests/openvino/test_modeling.py::OVModelForCausalLMIntegrationTest::test_multiple_inputs_24_phi - huggingface_hub.utils._errors.RepositoryNotFoundError: 401 Client Error. (Request ID: Root=1-66066c80-77cc281202da82206bf94efb;6b43617e-63e2-4432-95ce-1b591c2093f4)

Do you know which model can be used as replacement?

[echarlaix]

@echarlaix looks like phi model used in tests was removed from hub FAILED tests/openvino/test_modeling.py::OVModelForCausalLMIntegrationTest::test_multiple_inputs_24_phi - huggingface_hub.utils._errors.RepositoryNotFoundError: 401 Client Error. (Request ID: Root=1-66066c80-77cc281202da82206bf94efb;6b43617e-63e2-4432-95ce-1b591c2093f4)

Do you know which model can be used as replacement?

Let me check whether bumblebee-testing/tiny-random-PhiForCausalLM could be used instead

[echarlaix]

should be fixed in #643