[Pytorch] Warnings in check_set_window_size() trigger always

[Marks101]

Hello there,

the warnings in check_set_window_size() introduced in #960 seem to trigger all the time even if the input is actually correct and is not modified:

>>> check_set_window_size("causal", (-1, 0))
/virtualenv/lib/python3.10/site-packages/transformer_engine/pytorch/attention.py:3051: UserWarning: window_size should be (-1, 0) or (>=0, 0) for attn_mask_type=causal
  warnings.warn(
(-1, 0)

I think it might be more helpful if the warning is only issued if the input window size is actually modified.

Thanks for looking into this!

[cyanguwa]

See PR #1074.