staging: comedi: usbduxsigma: fix the ai/ao cmd->start_arg use for TRIG_INT

For both ai and ao commands this driver supports a cmd->start_src of
TRIG_NOW or TRIG_INT. The cmd->start_arg is trivially validated for
both sources to be 0.

For a TRIG_INT source, the cmd->start_arg is actually the valid
trig_num that is used by the async (*inttrig) callback.

Refactor the (*inttrig) functions so that the cmd->start_arg is used
to check the trig_num instead of the open coded values.

For aesthetics, remove some unnecessary comments in the (*do_cmd)
functions.
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/usbduxsigma.c

@@ -663,12 +663,13 @@ static int usbduxsigma_receive_cmd(struct comedi_device *dev, int command)
 
 static int usbduxsigma_ai_inttrig(struct comedi_device *dev,
 				  struct comedi_subdevice *s,
-				  unsigned int trignum)
+				  unsigned int trig_num)
 {
 	struct usbduxsigma_private *devpriv = dev->private;
+	struct comedi_cmd *cmd = &s->async->cmd;
 	int ret;
 
-	if (trignum != 0)
+	if (trig_num != cmd->start_arg)
 		return -EINVAL;
 
 	down(&devpriv->sem);
@@ -738,7 +739,6 @@ static int usbduxsigma_ai_cmd(struct comedi_device *dev,
 		}
 		s->async->inttrig = NULL;
 	} else {	/* TRIG_INT */
-		/* wait for an internal signal and submit the urbs later */
 		s->async->inttrig = usbduxsigma_ai_inttrig;
 	}
 
@@ -856,12 +856,13 @@ static int usbduxsigma_ao_insn_write(struct comedi_device *dev,
 
 static int usbduxsigma_ao_inttrig(struct comedi_device *dev,
 				  struct comedi_subdevice *s,
-				  unsigned int trignum)
+				  unsigned int trig_num)
 {
 	struct usbduxsigma_private *devpriv = dev->private;
+	struct comedi_cmd *cmd = &s->async->cmd;
 	int ret;
 
-	if (trignum != 0)
+	if (trig_num != cmd->start_arg)
 		return -EINVAL;
 
 	down(&devpriv->sem);
@@ -1027,7 +1028,6 @@ static int usbduxsigma_ao_cmd(struct comedi_device *dev,
 		}
 		s->async->inttrig = NULL;
 	} else {	/* TRIG_INT */
-		/* wait for an internal signal and submit the urbs later */
 		s->async->inttrig = usbduxsigma_ao_inttrig;
 	}