staging: comedi: refactor 8255 driver to remove forward declarations

Move the module_init/module_exit routines and the associated
struct comedi_driver variable to the end of the source. This is
more typical of how other drivers are written and removes the
need for the forward declarations.

Also, move the do_config function to remove needing to have
a forward declaration for that routine.

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