Updated SparseML callback for latest PyTorch Lightning

[clementpoiret]

What does this PR do?

It fixes an issue, where steps_per_epoch had to be positive. With recent pl lightning, it is -1 so it raises an error.

• Fix for max_steps (now defaults to -1), leading the callback to pass trainer.max_steps to steps_per_epoch, raising an error,
• Fix for deprecation of num_gpus, num_processes and tpu_cores. Those attributes will be deleted, and we should use num_devices instead. To avoid breaking changes, the old behavior stays the same if trainer has no num_devices attribute.

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[awaelchli]

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