staging: comedi: drivers: use comedi_legacy_detach() in simple drivers

Use the new comedi_legacy_detach() helper in the (*detach) to release
the I/O region requested by these drivers.

Since the (*detach) for these drivers only releases the region, remove
the private (*detach) functions and use comedi_legacy_detach() directly
for the (*detach).

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>