staging: comedi: adv_pci1723: remove comedi_device 'write_subdev' init

The comedi_device 'write_subdev' should only be initialized if the subdevice
supports async commands.

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>

drivers/staging/comedi/drivers/adv_pci1723.c

@@ -155,7 +155,6 @@ static int pci1723_auto_attach(struct comedi_device *dev,
 		return ret;
 
 	s = &dev->subdevices[0];
-	dev->write_subdev = s;
 	s->type		= COMEDI_SUBD_AO;
 	s->subdev_flags	= SDF_WRITABLE | SDF_GROUND | SDF_COMMON;
 	s->n_chan	= 8;