[Bugfix] Fix dsv4 deepgemm import

[wzhao18]

Purpose

Fix Dsv4 deepgemm import to use _import_deep_gemm(), which prioritizes loading from pip-installed version, instead of the hardcoded vllm.third_party.deep_gemm path. This aligns with the existing deep gemm import in the codebase, and avoids potentially importing different deepgemm modules during runtime.

Test Plan

Test Result

---

Essential Elements of an Effective PR Description Checklist

• The purpose of the PR, such as "Fix some issue (link existing issues this PR will resolve)".
• The test plan, such as providing test command.
• The test results, such as pasting the results comparison before and after, or e2e results
• (Optional) The necessary documentation update, such as updating supported_models.md and examples for a new model.

[claude]

Claude Code Review

This pull request is from a fork — automated review is disabled. A repository maintainer can comment @claude review to run a one-time review.

[wzhao18]

@ywang96 found this needed when testing the deep gemm versions.

[gemini-code-assist]

Code Review

This pull request refactors the deep_gemm import logic in deepseek_v4.py by replacing direct third-party imports with a call to the _import_deep_gemm utility function. Review feedback indicates that since this utility can return None, explicit checks should be added to prevent potential AttributeErrors and provide clearer ImportError messages. Additionally, it is suggested to refactor the duplicated import logic across multiple methods into a more maintainable helper or attribute.

[mergify]

This pull request has merge conflicts that must be resolved before it can be
merged. Please rebase the PR, @wzhao18.

https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/working-with-forks/syncing-a-fork