The previous version of this was pretty bad and caused a lot of
odd behevaiour to occur. We now abstract a lot of the allocation
behind a `template`d pool class that handles all of the memory
allocation.
The number of UHCI related files is starting to expand to the point
where it's best if we move this into their own subdirectory. It'll
also make it easier to manage when we decide to add some more
controller types (whenever that may be)
