staging: comedi: das1800: use comedi_legacy_detach()

Use the new comedi_legacy_detach() helper in the (*detach) to release
the first I/O region requested by this driver.

An additional I/O region is requested for some of the boards this driver
supports. The iobase for that region is stored in the private data so
that the (*detach) knows it needs to be released. Remove the extra
cleanup in the (*attach) that releases the first region.

For aesthetics, move the release of the additional region in the
(*detach) so it follows the (*attach) order.

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>