staging: comedi: amplc_dio200: use comedi_legacy_detach()

The I/O region used by this driver is always requested using
comedi_request_region(). The devpriv->io union is only used by
the common code shared by the legacy and PCI drivers.

Use the new comedi_legacy_detach() helper in the (*detach) to
release the I/O region requested by this driver. That function
will handle the proper sanity checking before releasing the
resource.

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>