feat: remove redundant codes under virt64, c906

[polarvid]

Fixed #9151

拉取/合并请求描述：(PR description)

[

为什么提交这份PR (why to submit this PR)

remove redundant codes under virt64, c906 (for those identical files)

你的解决方案是什么 (what is your solution)

Changes:

• create new folder name common64 and save all common codes of rv64
  inside

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

• BSP: QEMU virt64, persim M7, milk-v duo 256

• .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

[mysterywolf]

@polarvid 这个PR是否继续推进呀？

[polarvid]

@polarvid 这个PR是否继续推进呀？

近期会 Rebase 一下，测试下没什么问题就会取消草稿状态了。

[heyuanjie87]

测试成功

msh />mcrom
[I/app.filesystem] Dir / crom mount ok!
[I/app.filesystem] Dir /dev/shm tmp mount ok!
[I/app.filesystem] file system initialization done!

msh />mount sd0 /mnt elm
mount device sd0(elm) onto /mnt ... succeed!
msh />sbin/init
msh />[E/sal.skt] not find network interface device by protocol family(1).
[E/sal.skt] SAL socket protocol family input failed, return error -3.
/ # ./mnt/a.out
fpu
12.420000
/ #