Change attention mask type to uint8 for cudnn_flash_te

[Skylion007]

Description

This forces the dtype of the attention mask for TransfromerEngine to be uint8. This allows DeepSeekV3 and other models to run through TransformerEngine (using the nightly jax:maxtext container from 09-04-2025).

This is needed to pass assert added in TransformerEngine https://github.com/NVIDIA/TransformerEngine/blob/c47f329b2084406093124851a3aeecb935183def/transformer_engine/jax/cpp_extensions/softmax.py#L484 . This enables the MLA from DeepSeekV3 to not through an assert in TransformerEngine.

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Tests

Please describe how you tested this change, and include any instructions and/or
commands to reproduce.

I ran it locally on H200s and verified the assert is no longer an issue when using cudnn_attn_te as the attention implementation.

Checklist

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• I have made or will make corresponding changes to the doc if needed.

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[Skylion007]

SIgned the CLA