staging: comedi: adl_pci9111: clarify Step 2b of the (*do_cmdtest)

This step of the (*do_cmdtest) verifies that the selected trigger sources
are mutually compatible.

For this driver the scan_begin_src must be TRIG_FOLLOW or the same source
as the convert_src.

Simplify the logic to clarify this.
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/adl_pci9111.c

@@ -379,14 +379,10 @@ static int pci9111_ai_do_cmd_test(struct comedi_device *dev,
 
 	/* Step 2b : and mutually compatible */
 
-	if ((cmd->convert_src == TRIG_TIMER) &&
-	    !((cmd->scan_begin_src == TRIG_TIMER) ||
-	      (cmd->scan_begin_src == TRIG_FOLLOW)))
-		err |= -EINVAL;
-	if ((cmd->convert_src == TRIG_EXT) &&
-	    !((cmd->scan_begin_src == TRIG_EXT) ||
-	      (cmd->scan_begin_src == TRIG_FOLLOW)))
+	if (cmd->scan_begin_src != TRIG_FOLLOW) {
+		if (cmd->scan_begin_src != cmd->convert_src)
 			err |= -EINVAL;
+	}
 
 	if (err)
 		return 2;