[bsp] GD32F4xx: Add the ability to manually configure HXTAL clock par…

[Dimatcher]

…ameters

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:
  bsp/gd32/arm/gd32450z-eval

• .config:
  CONFIG_BSP_GD32_HXTAL_CLOCK_CFG=y
  CONFIG_BSP_GD32_SYSTEM_CLOCK=200000000
  CONFIG_BSP_GD32_CLOCK_PSC=8
  CONFIG_BSP_GD32_CLOCK_PLL_N=400
  CONFIG_BSP_GD32_CLOCK_PLL_P=2
  CONFIG_BSP_GD32_CLOCK_PLL_Q=9

• 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

[supperthomas]

这个是必须的吗？可以挪到board.c中吗？放这里，不利于后期sdk更新，而且一般不应该改到厂商的SDK