staging: comedi: serial2002: hookup the (*open) and (*close) last

For aesthetic reasons, hookup the comedi_device (*open) and (*close)
functions after everything else in the attach has succeeded.

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