Improvements to rt-spark serial_v2 support

[rcitach]

拉取/合并请求描述：(PR description)

[

为什么提交这份PR (why to submit this PR)

你的解决方案是什么 (what is your solution)

请提供验证的bsp和config (provide the config and bsp)

• BSP:

• .config:

• action:

]

当前拉取/合并请求的状态 Intent for your PR

必须选择一项 Choose one (Mandatory):

• 本拉取/合并请求是一个草稿版本 This PR is for a code-review and is intended to get feedback
• 本拉取/合并请求是一个成熟版本 This PR is mature, and ready to be integrated into the repo

代码质量 Code Quality：

我在这个拉取/合并请求中已经考虑了 As part of this pull request, I've considered the following:

• 已经仔细查看过代码改动的对比 Already check the difference between PR and old code
• 代码风格正确，包括缩进空格，命名及其他风格 Style guide is adhered to, including spacing, naming and other styles
• 没有垃圾代码，代码尽量精简，不包含#if 0代码，不包含已经被注释了的代码 All redundant code is removed and cleaned up
• 所有变更均有原因及合理的，并且不会影响到其他软件组件代码或BSP All modifications are justified and not affect other components or BSP
• 对难懂代码均提供对应的注释 I've commented appropriately where code is tricky
• 代码是高质量的 Code in this PR is of high quality
• 已经使用formatting 等源码格式化工具确保格式符合RT-Thread代码规范 This PR complies with RT-Thread code specification
• 如果是新增bsp, 已经添加ci检查到.github/workflows/bsp_buildings.yml 详细请参考链接BSP自查

[github-actions]

📌 Code Review Assignment

🏷️ Tag: bsp_rt-spark

Reviewers: Rbb666 kurisaW

Changed Files (Click to expand)

• bsp/stm32/stm32f407-rt-spark/board/Kconfig

🏷️ Tag: bsp_stm32

Reviewers: Liang1795 hamburger-os wdfk-prog

Changed Files (Click to expand)

• bsp/stm32/stm32f407-rt-spark/board/Kconfig

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📊 Current Review Status (Last Updated: 2025-07-18 18:15 CST)

• ⌛ Liang1795 Pending Review
• ⌛ Rbb666 Pending Review
• ⌛ hamburger-os Pending Review
• ⌛ kurisaW Pending Review
• ⌛ wdfk-prog Pending Review

---

📝 Review Instructions

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   Maintainers can refresh the review status by clicking here: 🔄 Refresh Status

2. 确认审核通过后评论 LGTM/lgtm
   Comment LGTM/lgtm after confirming approval

3. PR合并前需至少一位维护者确认
   PR must be confirmed by at least one maintainer before merging

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ℹ️ Refresh CI status operation requires repository Write permission.

[wdfk-prog]

LGTM