Remove reference to sys/dev/dpt/dpt_control.c.  It was removed back in 2001 after having
never been updated for CAM changes in 1998.
Remove dpt_isa.c and commented out references to it.  It was never connected
to the build in either sys/conf/files* or sys/modules/dpt/Makefile.  Also,
it was denoted as "doesn't quite work yet" when the file was initially added
(which may account for it never having been hooked up to the build).