staging: comedi: pcl818: use cfc_bytes_per_scan()

Use the comedi_fc helper to get the number of bytes per scan.
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/pcl818.c

@@ -353,7 +353,7 @@ static void pcl818_ai_setup_dma(struct comedi_device *dev,
 	disable_dma(devpriv->dma);	/*  disable dma */
 	bytes = devpriv->hwdmasize;
 	if (cmd->stop_src == TRIG_COUNT) {
-		bytes = cmd->chanlist_len * cmd->stop_arg * sizeof(short);
+		bytes = cmd->stop_arg * cfc_bytes_per_scan(s);
 		devpriv->dma_runs_to_end = bytes / devpriv->hwdmasize;
 		devpriv->last_dma_run = bytes % devpriv->hwdmasize;
 		devpriv->dma_runs_to_end--;