Previous link to provide details of `0x80 debug port` is removed, which
could no longer be found on intel site [1]. Use snapshot found in web
archive [2] to fix this link.
Format `debug-port.md` using `mdformat` with GitHub Flavored Markdown
(GFM).
[1] https://www.intel.com/content/www/us/en/homepage.html
[2] https://web.archive.org
Signed-off-by: Ruoqing He <heruoqing@iscas.ac.cn>