staging: comedi: gsc_hpdi: move the (*auto_attach) and (*detach) functions

Move these functions closer to the comedi_driver declaration. This removes
the need for one of the forward declarations.

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>