staging: comedi: 8255: provide common defines for registers

There are a couple comedi drivers that duplicate some of the register
defines used by the 8255 module. Move these defines into the header
so the duplication can be removed.

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>