timeout()/untimeout() API:
- Clients supply callout handle storage, thus eliminating problems of
resource allocation.
- Insertion and removal of callouts is constant time, important as
this facility is used quite a lot in the kernel.
The old timeout()/untimeout() API has been removed from the kernel.
was being initialized to a KVA, when we really wanted a DMA address. Change
the code to allocate the overrun buffer with the control blocks, and
properly initialize overrun_buf.
Note that overrun_buf cannot actually be shared between all boards; DMA safe
memory could vary from bus to bus.
Garbage-collect two functions which are no longer used because of the
above changes.
