remove netbsd and openbsd code
- we (plasma) do not support either
- the code hasn't been touched in ages
- parts of code are under public domain, which has somewhat unclear impact when another person adds code under subject of a jurisdiction that doesn't have that particular legal concept
- the previous point then also complicates transitioning to spdx tags
(the relevant kcms are possibly not long for this world anyway. they can pretty much all be replaced by cheap CLI modules, rendering the code moot one way or another)