net: dsa: sja1105: Fix missing unlock on error in sk_buff()

Add the missing unlock before return from function sk_buff()
in the error handling case.

Fixes: f3097be21b ("net: dsa: sja1105: Add a state machine for RX timestamping")
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Reviewed-by: Vivien Didelot <vivien.didelot@gmail.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/dsa/tag_sja1105.c

@@ -216,6 +216,7 @@ static struct sk_buff
 		if (!skb) {
 			dev_err_ratelimited(dp->ds->dev,
 					    "Failed to copy stampable skb\n");
+			spin_unlock(&sp->data->meta_lock);
 			return NULL;
 		}
 		sja1105_transfer_meta(skb, meta);