staging: comedi: aio_iiro_16: fix subdevice 0 'type'

Subdevice 0 is a digial output not a digital I/O subdevice.

Fix the type and, for aesthetics, rename the (*insn_bits) function used
to set the outputs.

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>