Staging: comedi: kcomedilib: make it typesafe

If we really are passing in a struct comedi_device, then say we are,
don't mess around with void pointers for no reason.

This also fixes up the comedi_bond.c driver, which is the only
user of the kcomedilib code.

Cc: Ian Abbott <abbotti@mev.co.uk>
Cc: Frank Mori Hess <fmhess@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>