rewrite the workaround about Soft Lockup

the “soft lockup - CPU#X stuck for 22s” is affecting several computers (some of them are listed in the comment of #15774 (closed), but there are more, like the MSI Ghost GS60). usually the workarounds proposed for the xps 9560 are working on those computers, but the users are having trouble finding it by themselves due to the lack of details in the known issue entry (https://tails.boum.org/support/known_issues/index.en.html#index14h3).

it would be really great if, at least, the error message was specified, and if there was an anchor to that specific entry.

Related issues

• Blocks #15941 (closed)

Original created by @goupille on 16715 (Redmine)