staging: comedi: pcl812: use comedi_fc helpers to validate timer arg

Use the comedi_fc helper cfc_check_trigger_arg_is() to validate the
trigger argument when the source is TRIG_TIMER.

The minimum test is not needed, this was already validated in Step 3.

All the arguments are unsigned int, change the local variable to an
unsigned int and rename it for aesthetic reasons.
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/pcl812.c

@@ -721,7 +721,7 @@ static int pcl812_ai_cmdtest(struct comedi_device *dev,
 	struct pcl812_private *devpriv = dev->private;
 	int err = 0;
 	unsigned int flags;
-	int tmp;
+	unsigned int arg;
 
 	/* Step 1 : check if triggers are trivially valid */
 
@@ -774,15 +774,12 @@ static int pcl812_ai_cmdtest(struct comedi_device *dev,
 	/* step 4: fix up any arguments */
 
 	if (cmd->convert_src == TRIG_TIMER) {
-		tmp = cmd->convert_arg;
+		arg = cmd->convert_arg;
 		i8253_cascade_ns_to_timer(I8254_OSC_BASE_2MHZ,
 					  &devpriv->divisor1,
 					  &devpriv->divisor2,
-					  &cmd->convert_arg, cmd->flags);
-		if (cmd->convert_arg < board->ai_ns_min)
-			cmd->convert_arg = board->ai_ns_min;
-		if (tmp != cmd->convert_arg)
-			err++;
+					  &arg, cmd->flags);
+		err |= cfc_check_trigger_arg_is(&cmd->convert_arg, arg);
 	}
 
 	if (err)