net: dsa: b53: always rejoin default untagged VLAN on bridge leave

While JOIN_ALL_VLAN allows to join all VLANs, we still need to keep the
default VLAN enabled so that untagged traffic stays untagged.

So rejoin the default VLAN even for switches with JOIN_ALL_VLAN support.

Fixes: 48aea33 ("net: dsa: b53: Add JOIN_ALL_VLAN support")
Signed-off-by: Jonas Gorski <jonas.gorski@gmail.com>
Tested-by: Florian Fainelli <florian.fainelli@broadcom.com>
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
Link: https://patch.msgid.link/20250429201710.330937-7-jonas.gorski@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: KanjiMonster

drivers/net/dsa/b53/b53_common.c

@@ -2021,12 +2021,12 @@ void b53_br_leave(struct dsa_switch *ds, int port, struct dsa_bridge bridge)
 		if (!(reg & BIT(cpu_port)))
 			reg |= BIT(cpu_port);
 		b53_write16(dev, B53_VLAN_PAGE, B53_JOIN_ALL_VLAN_EN, reg);
-	} else {
-		b53_get_vlan_entry(dev, pvid, vl);
-		vl->members |= BIT(port) | BIT(cpu_port);
-		vl->untag |= BIT(port) | BIT(cpu_port);
-		b53_set_vlan_entry(dev, pvid, vl);
 	}
+
+	b53_get_vlan_entry(dev, pvid, vl);
+	vl->members |= BIT(port) | BIT(cpu_port);
+	vl->untag |= BIT(port) | BIT(cpu_port);
+	b53_set_vlan_entry(dev, pvid, vl);
 }
 EXPORT_SYMBOL(b53_br_leave);