Fix cuda index issue in cache allocator

[SunMarc]

What does this PR do?

This PR fixes cache allocator function when querying the max-memory available on cuda devices. Currently, it doesn't work for torch <= 2.4.1 due to torch.cuda.mem_get_info raising an issue if we pass a device without an index.

Traceback returned for a loading a model like gpt2 with device_map="cuda"

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/marc/transformers/src/transformers/models/auto/auto_factory.py", line 573, in from_pretrained
    return model_class.from_pretrained(
  File "/home/marc/transformers/src/transformers/modeling_utils.py", line 272, in _wrapper
    return func(*args, **kwargs)
  File "/home/marc/transformers/src/transformers/modeling_utils.py", line 4474, in from_pretrained
    ) = cls._load_pretrained_model(
  File "/home/marc/transformers/src/transformers/modeling_utils.py", line 4859, in _load_pretrained_model
    caching_allocator_warmup(model_to_load, expanded_device_map)
  File "/home/marc/transformers/src/transformers/modeling_utils.py", line 5870, in caching_allocator_warmup
    index = device.index if device.index is not None else 0
  File "/home/marc/anaconda3/envs/llama-export/lib/python3.10/site-packages/torch/cuda/memory.py", line 684, in mem_get_info
    device = _get_device_index(device)
  File "/home/marc/anaconda3/envs/llama-export/lib/python3.10/site-packages/torch/cuda/_utils.py", line 38, in _get_device_index
    return _torch_get_device_index(device, optional, allow_cpu)
  File "/home/marc/anaconda3/envs/llama-export/lib/python3.10/site-packages/torch/_utils.py", line 803, in _get_device_index
    raise ValueError(
ValueError: Expected a torch.device with a specified index or an integer, but got:cuda

cc @winglian

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[Cyrilvallez]

Thanks a lot for fixing!