staging: comedi: initialize subdevice s->io_bits in postconfig

The subdevice 'io_bits' is a bit mask of the i/o configuration for
digital subdevices. '0' values indicate that a channel is configured
as an input and '1' values that the channel is an output. Since the
subdevice data is kzalloc()'d, all channels default as inputs.

Modify __comedi_device_postconfig() so that 'io_bits' is correctly
initialized for Digital Output subdevices.

Remove all the unnecessary initializations of 's->io_bits' from the
drivers. Also, remove the unnecessary initialization of the 's->state'.

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>