staging: comedi: hwdrv_apci3120: use sample manipulation helpers

Use the recently added sample manipulation helpers to remove the hardcoded
assumption of the sample size.
Signed-off-by: NH Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: NIan Abbott <abbotti@mev.co.uk>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/comedi/drivers/addi-data/hwdrv_apci3120.c

@@ -947,7 +947,9 @@ static int apci3120_cyclic_ai(int mode,
 		/* If DMA Enabled */
 		struct apci3120_dmabuf *dmabuf0 = &devpriv->dmabuf[0];
 		struct apci3120_dmabuf *dmabuf1 = &devpriv->dmabuf[1];
-		unsigned int scan_bytes = cmd->scan_end_arg * sizeof(short);
+		unsigned int scan_bytes;
+
+		scan_bytes = comedi_samples_to_bytes(s, cmd->scan_end_arg);
 
 		devpriv->b_InterruptMode = APCI3120_DMA_MODE;