net: dsa: tag_qca: return early if dev is not found

Currently checksum is recalculated and dsa tag stripped even if we later
don't find the dev.

To improve code, exit early if we don't find the dev and skip additional
operation on the skb since it will be freed anyway.
Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
Link: https://lore.kernel.org/r/20230730074113.21889-1-ansuelsmth@gmail.comSigned-off-by: Paolo Abeni <pabeni@redhat.com>

net/dsa/tag_qca.c

@@ -75,10 +75,6 @@ static struct sk_buff *qca_tag_rcv(struct sk_buff *skb, struct net_device *dev)
 		return NULL;
 	}
 
-	/* Remove QCA tag and recalculate checksum */
-	skb_pull_rcsum(skb, QCA_HDR_LEN);
-	dsa_strip_etype_header(skb, QCA_HDR_LEN);
-
 	/* Get source port information */
 	port = FIELD_GET(QCA_HDR_RECV_SOURCE_PORT, hdr);
 
@@ -86,6 +82,10 @@ static struct sk_buff *qca_tag_rcv(struct sk_buff *skb, struct net_device *dev)
 	if (!skb->dev)
 		return NULL;
 
+	/* Remove QCA tag and recalculate checksum */
+	skb_pull_rcsum(skb, QCA_HDR_LEN);
+	dsa_strip_etype_header(skb, QCA_HDR_LEN);
+
 	return skb;
 }