staging: comedi: das08,das08_cs: Move das08_cs_boards[]

Move `das08_cs_boards[]` from "das08.c" to "das08_cs.c" and make it
static const.  It no longer refers to anything in "das08.c" and no
longer needs to be exported.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>