staging: comedi: fix up missing whitespace in comment

I noticed this missing whitespace in a comment inside ni_mio_common.c
Signed-off-by: Garrit Franke <garritfranke@gmail.com>
Link: https://lore.kernel.org/r/20200615135541.46986-1-garritfranke@gmail.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/comedi/drivers/ni_mio_common.c

@@ -2390,7 +2390,7 @@ static int ni_ai_cmd(struct comedi_device *dev, struct comedi_subdevice *s)
 #endif
 			break;
 		case AIMODE_SAMPLE:
-			/*generate FIFO interrupts on non-empty */
+			/* generate FIFO interrupts on non-empty */
 			ni_stc_writew(dev, NISTC_AI_MODE3_FIFO_MODE_NE,
 				      NISTC_AI_MODE3_REG);
 			break;