Fix prebuild for cktile moe kernel

[Rohan138]

Motivation

While working on https://github.com/ROCm/vllm/pull/808/files, we've found that building the aiter wheel then linking it into the final docker build stage leads to a broken build, which does not occur when building the library in-place. cc @dllehr-amd @zhiding512

It looks like the CKtile 2stage MOE was not registered in pybind when it was ported over from 355_wip: https://github.com/ROCm/aiter/blob/355_wip/csrc/rocm_ops.cpp#L80; linking it fixes the issue.

Also updated the CK 2stage MOE to use FLATMM_HIP_CLANG_PATH.

Technical Details

Test Plan

Test Result

Submission Checklist

• Look over the contributing guidelines at https://github.com/ROCm/ROCm/blob/develop/CONTRIBUTING.md#pull-requests.

[zhiding512]

LGTM

[Copilot]

Pull Request Overview

This PR fixes a missing pybind registration for the CKtile 2-stage MOE kernel that was not properly registered when ported from the 355_wip branch. The fix enables the CKtile MOE functions to be accessible from Python.

• Adds the missing header include for moe_cktile2stages.h
• Registers the MOE_CKTILE_2STAGES_PYBIND macro to expose cktile_moe_gemm1 and cktile_moe_gemm2 functions

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[Rohan138]

@zhiding512 / @valarLip PTAL, can we merge to unblock vllm/355_wip? Unrelated CI failures due to git ssh outage earlier today