[media] smiapp: Take mutex during PLL update in sensor initialisation

The mutex does not serialise anything in this case but avoids a lockdep
warning from the control framework.

Cc: stable@vger.kernel.org
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

drivers/media/i2c/smiapp/smiapp-core.c

@@ -2677,7 +2677,9 @@ static int smiapp_registered(struct v4l2_subdev *subdev)
 		pll->flags |= SMIAPP_PLL_FLAG_NO_OP_CLOCKS;
 	pll->scale_n = sensor->limits[SMIAPP_LIMIT_SCALER_N_MIN];
 
+	mutex_lock(&sensor->mutex);
 	rval = smiapp_update_mode(sensor);
+	mutex_unlock(&sensor->mutex);
 	if (rval) {
 		dev_err(&client->dev, "update mode failed\n");
 		goto out_nvm_release;