config(8) doesn't know anything about scsi devices like it used to, remove

config(8) doesn't know anything about scsi devices like it used to, remove
the misleading comments to that effect.
Prune bogus 'at foo?' (smbus, iicbus, ppbus) appendages on things that
they are meaningless for.  It was just eye candy and wasn't used by
anything in the tree.  The interconnects were defined by the drivers
themselves and auto discovery.
(The new ppbus code may change this if it uses the resource_get_*() calls
 to find it's configured children if self discovery isn't possible)