media: i2c: imx258: Drop check for reentrant .s_stream()

The subdev .s_stream() operation shall not be called to start streaming
on an already started subdev, or stop streaming on a stopped subdev.
Remove the check that guards against that condition.

Signed-off-by: Laurent Pinchart <[e-mail]>
Signed-off-by: Sakari Ailus <[e-mail]>
Signed-off-by: Hans Verkuil <[e-mail]>

drivers/media/i2c/imx258.c

···
 	int ret = 0;
 
 	mutex_lock(&imx258->mutex);
-	if (imx258->streaming == enable) {
-		mutex_unlock(&imx258->mutex);
-		return 0;
-	}
 
 	if (enable) {
 		ret = pm_runtime_resume_and_get(&client->dev);