[ROCm] support topk_softplus for all number of experts

[tjtanaa]

Purpose

Add full support of topk_softplus on ROCm

Test Plan

Temporary widen the num_expert cases. I didn't widen the case to align with CUDA and also to reduce the unit test duration.

Test Result

================ 3240 passed, 16 warnings in 1297.93s (0:21:37) ================

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