media: mt9m111: add streaming check to set_fmt

Currently set_fmt don't care about the streaming status, so the format
can be changed during streaming. This can lead into wrong behaviours.

Check if the device is already streaming and return -EBUSY to avoid
wrong behaviours.
Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
Signed-off-by: Marco Felsch <m.felsch@pengutronix.de>
Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

drivers/media/i2c/mt9m111.c

@@ -563,6 +563,9 @@ static int mt9m111_set_fmt(struct v4l2_subdev *sd,
 	bool bayer;
 	int ret;
 
+	if (mt9m111->is_streaming)
+		return -EBUSY;
+
 	if (format->pad)
 		return -EINVAL;