staging: comedi: ni_mio_common: remove DEBUG_DIO messages

Defining DEBUG_DIO simply enables some function trace messages. These are
just added noise. Remove them.

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>