staging: comedi: dt282x: remove sanity checks of 's->async->prealloc_buf'

The comedi core sanity checks that the subdevice has a buffer allocated
before allowing an async command to start. The helper functions in comedi_buf
will also sanity check the buffer as a side effect of the 'alloc' helpers
with reading or writing data for the buffer.

Remove the unnecessary sanity checks in the ai/ao dma interrupt handlers.
This will allow the handlers to disable the dma and then fail when they
try to read/write the buffer. Currently dma is left enabled due to the
sanity checks.
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/dt282x.c

@@ -471,11 +471,6 @@ static void dt282x_ao_dma_interrupt(struct comedi_device *dev)
 
 	outw(devpriv->supcsr | DT2821_CLRDMADNE, dev->iobase + DT2821_SUPCSR);
 
-	if (!s->async->prealloc_buf) {
-		dev_err(dev->class_dev, "no buffer in %s\n", __func__);
-		return;
-	}
-
 	i = devpriv->current_dma_index;
 	ptr = devpriv->dma[i].buf;
 
@@ -504,11 +499,6 @@ static void dt282x_ai_dma_interrupt(struct comedi_device *dev)
 
 	outw(devpriv->supcsr | DT2821_CLRDMADNE, dev->iobase + DT2821_SUPCSR);
 
-	if (!s->async->prealloc_buf) {
-		dev_err(dev->class_dev, "no buffer in %s\n", __func__);
-		return;
-	}
-
 	i = devpriv->current_dma_index;
 	ptr = devpriv->dma[i].buf;
 	size = devpriv->dma[i].size;