[Bugfix][Kernel] Prevent integer overflow in fp8 dynamic per-token quantize kernel

[tlrmchlsmth]

After seeing #9391, I ran grep -r "token_idx \* hidden_size" csrc, and found that the same 32-bit integer overflow may happen in the fp8 dynamic quantize kernel as well.

This PR prevents this from happening by using int64_t instead

[github-actions]

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