docs/develop: More reorganization.

* There is now a 'busses' folder, and the extant USB/SDHCI/Bluetooth/etc.
docs now live in it, instead of various other places.
* kernel/ports is now kernel/a

docs/develop: More reorganization.

* There is now a 'busses' folder, and the extant USB/SDHCI/Bluetooth/etc.
docs now live in it, instead of various other places.
* kernel/ports is now kernel/arch, like it is in src/system.
SPARC documentation is now in there, too.
* VM files (these are rather outdated) are now in kernel/vm.
* SCSI ASC info removed, this is easily available online and
it doesn't seem to be very relevant.

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