staging: comedi: ni_660x: default DIO channels with subdevice init

For aesthetics, move the initialization of the default routing for the
DIO channels so it happens when the subdevice is initialized.

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>