staging: comedi: comedidev.h: make comedi_board() parameter const

The inline function `comedi_board(dev)` merely returns `dev->board_ptr`.
It does not modify any members of `*dev` so make its parameter a const
pointer.
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/comedi/comedidev.h

@@ -247,7 +247,7 @@ struct comedi_device {
 	void (*close) (struct comedi_device *dev);
 };
 
-static inline const void *comedi_board(struct comedi_device *dev)
+static inline const void *comedi_board(const struct comedi_device *dev)
 {
 	return dev->board_ptr;
 }