staging: comedi: ni_mio_common: create device-global access to tio

Adds tio sub-devices of ni_mio_common supported hardware to the
implementation of test_route, connect_route, disconnect_route.  This change
delegates the actual functionality to the ni_tio module.

Signed-off-by: Spencer E. Olson <olsonse@umich.edu>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>