staging: comedi: addi_apci_1032: add comedi driver comment

Add a comedi driver comment in a form suitable for importing into
Comedilib documentation.  The information about the change-of-state
subdevice has been pulled from other comments in the driver.

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>