fix: output router capture wrong router logits in qwen moe models
Author: ITcarrot
Pull request: yes

# What does this PR do?

This PR fixes a bug in the router implementation of several MoE models (Qwen Moe like models, `Olmoe`, `FlexOlmo`). 

Previously, the raw `router_logits` were being overwritten by the result of the softmax operation:
```python
router_logits = F.linear(hidden_states, self.weight)
router_logits = torch.nn.functional.softmax(router_logits, dtype=torch.float, dim=-1)
```
This behavior destroys the raw logits information, which is often required for:
1. Casting returned `router_top_value` back to input type in `router_top_value = router_top_value.to(router_logits.dtype)`
2. Calculating auxiliary losses (e.g., load balancing loss) which typically operate on raw logits.
3. Returning correct router_logits in the model output if requested.

## Before submitting
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- [ ] Did you write any new necessary tests?


## Who can review?

Anyone in the community is free to review the PR once the tests have passed. Feel free to tag
members/contributors who may be interested in your PR.

@Cyrilvallez @IlyasMoutawwakil 

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Comments:
**[For maintainers]** Suggested jobs to run (before merge)

run-slow: flex_olmo, olmoe, qwen2_moe, qwen3_moe, qwen3_next, qwen3_omni_moe