NPU adaption for RMSNorm

[leisuzz]

What does this PR do?

Added NPU RMSNorm function to get the better performance for NPU devices

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[leisuzz]

@sayakpaul Please take a look at this PR, thanks for your help!

[HuggingFaceDocBuilderDev]

The docs for this PR live here. All of your documentation changes will be reflected on that endpoint. The docs are available until 30 days after the last update.

[yiyixuxu]

thanks!

[hlky]

Thanks @leisuzz. Would be nice to check the numerical accuracy of this when we start adding NPU to CI.

[leisuzz]

Hi @hlky, I've already checked the accuracy of the npu RMSnorm. It didn't affect the accuracy of the result (loss are the same between the two methods in NPU).

[hlky]

That's great, thanks for checking @leisuzz.