[bsp/xuantie] 添加E901BSP

[MuChenger]

拉取/合并请求描述：(PR description)

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为什么提交这份PR (why to submit this PR)

添加E901 系列BSP的支持

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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/ALL_BSP_COMPILE.json 详细请参考链接BSP自查

[github-actions]

👋 感谢您对 RT-Thread 的贡献！Thank you for your contribution to RT-Thread!

为确保代码符合 RT-Thread 的编码规范，请在你的仓库中执行以下步骤运行代码格式化工作流（如果格式化CI运行失败）。
To ensure your code complies with RT-Thread's coding style, please run the code formatting workflow by following the steps below (If the formatting of CI fails to run).

---

🛠 操作步骤 | Steps

1. 前往 Actions 页面 | Go to the Actions page
   点击进入工作流 → | Click to open workflow →

2. 点击 Run workflow | Click Run workflow

• 设置需排除的文件/目录（目录请以"/"结尾）
  Set files/directories to exclude (directories should end with "/")
• 将目标分支设置为 \ Set the target branch to：xuantie_e901
• 设置PR number为 \ Set the PR number to：10836

3. 等待工作流完成 | Wait for the workflow to complete
   格式化后的代码将自动推送至你的分支。
   The formatted code will be automatically pushed to your branch.

完成后，提交将自动更新至 xuantie_e901 分支，关联的 Pull Request 也会同步更新。
Once completed, commits will be pushed to the xuantie_e901 branch automatically, and the related Pull Request will be updated.

如有问题欢迎联系我们，再次感谢您的贡献！💐
If you have any questions, feel free to reach out. Thanks again for your contribution!

[Copilot]

Pull Request Overview

This PR adds Board Support Package (BSP) support for the XuanTie E901 series processors, a RISC-V based embedded CPU family. The changes primarily involve adding configuration files, startup code, vector tables, and CSI (Chip Support Interface) library updates to support various E901 CPU variants including e901plus and e901 with different feature sets.

Key Changes

• Added complete E901 BSP implementation with board initialization, startup code, and interrupt handling
• Extended CSI library support for E901/E901Plus CPU variants across multiple architecture files
• Added toolchain configuration and build system support for E901 series

Reviewed Changes

Copilot reviewed 41 out of 45 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
bsp/xuantie/smartl/e901/board/*	Board initialization and hardware configuration for E901
bsp/xuantie/smartl/e901/*.py, *.h, *.bat	Build configuration, RT-Thread config, and development utilities
bsp/xuantie/libraries/.../csi/csi2/include/core/*	CSI core library updates adding E901 CPU support and fixing code style
bsp/xuantie/libraries/.../chip_riscv_dummy/src/arch/e901/*	E901-specific startup, vector table, trap handling, and system initialization
bsp/xuantie/libraries/.../chip_riscv_dummy/src/sys/feature.c	CPU feature initialization for different XuanTie processor variants

[Copilot]

English: Magic numbers like 0x103f and 0x3 should be defined as named constants with descriptive comments explaining their meaning for better code maintainability.
中文:像 0x103f 和 0x3 这样的魔术数字应该定义为具有描述性注释的命名常量,以解释它们的含义,从而提高代码可维护性。

[Rbb666]

@MuChenger CI看护也麻烦添加下吧