[CK_TILE] Use FLOAT_TO_BFLOAT16=3 for streamk extended tests

[DDEle]

Proposed changes

As title. It helps to avoid recent CI error on gfx90a. Related PR:

• [CK_TILE] Remove Old CK Tile Stream-K Artifacts #3202
• [CK_TILE] Refine FP32 => FP16/BF16 Conversion #3215

Checklist

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• I have added tests relevant to the introduced functionality, and the unit tests are passing locally
• I have added the test to REGRESSION_TESTS list defined at the top of CMakeLists.txt in tests/CMakeLists.txt, IF the test takes more than 30 seconds to run.
• I have added inline documentation which enables the maintainers with understanding the motivation
• I have removed the stale documentation which is no longer relevant after this pull request
• (If this change is user-facing) I have added release notes which provide the end users with a brief summary of the improvement from this pull request
• I have run clang-format on all changed files
• Any dependent changes have been merged

[DDEle]

Close as #3269 fixed the root problem.