[ROCm] enable moe topk softmax in amd

[yiakwy-xpu-ml-framework-team]

Motivation

Follow up of #4302

Modifications

• bench test

Checklist

• Format your code according to the Code Formatting with Pre-Commit.
• Add unit tests as outlined in the Running Unit Tests.
• Update documentation / docstrings / example tutorials as needed, according to Writing Documentation.
• Provide throughput / latency benchmark results and accuracy evaluation results as needed, according to Benchmark and Profiling and Accuracy Results.
• For reviewers: If you haven't made any contributions to this PR and are only assisting with merging the main branch, please remove yourself as a co-author when merging the PR.
• Please feel free to join our Slack channel at https://slack.sglang.ai to discuss your PR.

[yiakwy-xpu-ml-framework-team]

@HaiShaw

[yiakwy-xpu-ml-framework-team]

Plan to enable it in SGLang critical path after merge, see #4439

[BBuf]

I think we can merge this PR, as the only change is the export of amd topk_softmax interface. cc @zhyncs