[media] media: stk1160: Ignore unchanged standard set

This commit adds an early check to vidioc_s_std() to detect if the
new and current standards are equal, and exit with success in that
case.
This is needed to prevent userspace applications that might attempt
to re-set the same standard from failing if that's done when streaming
has started.

Signed-off-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>

drivers/media/usb/stk1160/stk1160-v4l.c

@@ -379,6 +379,9 @@ static int vidioc_s_std(struct file *file, void *priv, v4l2_std_id norm)
 	struct stk1160 *dev = video_drvdata(file);
 	struct vb2_queue *q = &dev->vb_vidq;
 
+	if (dev->norm == norm)
+		return 0;
+
 	if (vb2_is_busy(q))
 		return -EBUSY;