and used by uart(4) for the channel conflicted with the port offset for
the Z8530. The Z8530 has the channels reversed (i.e. channel B is at
offset 0 and channel A is at offset 4). Assign the port offsets in the
right order so that uart(4) will properly attach to the channels.
Submitted by: Marius Strobl <marius@alchemy.franken.de>