net: dpaa: fix device leak when querying time stamp info

Make sure to drop the reference to the ptp device taken by
of_find_device_by_node() when querying the time stamping capabilities.

Note that holding a reference to the ptp device does not prevent its
driver data from going away.

Fixes: 17ae0b0 ("dpaa_eth: add the get_ts_info interface for ethtool")
Cc: [email protected]	# 4.19
Cc: Yangbo Lu <[email protected]>
Signed-off-by: Johan Hovold <[email protected]>
Reviewed-by: Simon Horman <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

Author: jhovold

drivers/net/ethernet/freescale/dpaa/dpaa_ethtool.c

@@ -371,8 +371,10 @@ static int dpaa_get_ts_info(struct net_device *net_dev,
 		of_node_put(ptp_node);
 	}
 
-	if (ptp_dev)
+	if (ptp_dev) {
 		ptp = platform_get_drvdata(ptp_dev);
+		put_device(&ptp_dev->dev);
+	}
 
 	if (ptp)
 		info->phc_index = ptp->phc_index;