staging: comedi: amplc_dio200.h: make self-reliant

The Comedi "amplc_dio200.h" header file included by drivers for Amplicon
DIO200 series cards does not compile cleanly when it is the first header
included by the ".c" file.  It uses `struct comedi_device *` in the
parameter lists of some function prototypes, so just declare `struct
comedi_device` as an incomplete type.  It also uses `bool`, so include
<linux/types.h> to declare it.

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