net: fix sock_timestamping_bind_phc() to release device

Don't forget to release the device in sock_timestamping_bind_phc() after
it was used to get the vclock indices.

Fixes: d463126e23 ("net: sock: extend SO_TIMESTAMPING for PHC binding")
Signed-off-by: Miroslav Lichvar <mlichvar@redhat.com>
Cc: Yangbo Lu <yangbo.lu@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/sock.c

@@ -844,6 +844,8 @@ static int sock_timestamping_bind_phc(struct sock *sk, int phc_index)
 	}
 
 	num = ethtool_get_phc_vclocks(dev, &vclock_index);
+	dev_put(dev);
+
 	for (i = 0; i < num; i++) {
 		if (*(vclock_index + i) == phc_index) {
 			match = true;