net: dsa: tag_qca: use the dsa_xmit_port_mask() helper

The "qca" tagging protocol populates a bit mask for the TX ports, so we
can use dsa_xmit_port_mask() to centralize the decision of how to set
that field.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Link: https://patch.msgid.link/20251127120902.292555-10-vladimir.oltean@nxp.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: vladimiroltean

net/dsa/tag_qca.c

@@ -14,7 +14,6 @@
 
 static struct sk_buff *qca_tag_xmit(struct sk_buff *skb, struct net_device *dev)
 {
-	struct dsa_port *dp = dsa_user_to_port(dev);
 	__be16 *phdr;
 	u16 hdr;
 
@@ -26,7 +25,7 @@ static struct sk_buff *qca_tag_xmit(struct sk_buff *skb, struct net_device *dev)
 	/* Set the version field, and set destination port information */
 	hdr = FIELD_PREP(QCA_HDR_XMIT_VERSION, QCA_HDR_VERSION);
 	hdr |= QCA_HDR_XMIT_FROM_CPU;
-	hdr |= FIELD_PREP(QCA_HDR_XMIT_DP_BIT, BIT(dp->index));
+	hdr |= FIELD_PREP(QCA_HDR_XMIT_DP_BIT, dsa_xmit_port_mask(skb, dev));
 
 	*phdr = htons(hdr);