net: dsa: mv88e6xxx: Unlock on error in mv88e6xxx_port_bridge_join()

Call mv88e6xxx_reg_unlock(chip) before returning on this error path.

Fixes: 7af4a361 ("net: dsa: mv88e6xxx: Improve isolation of standalone ports")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/dsa/mv88e6xxx/chip.c

@@ -2602,7 +2602,7 @@ static int mv88e6xxx_port_bridge_join(struct dsa_switch *ds, int port,
 
 	err = mv88e6xxx_port_set_map_da(chip, port, true);
 	if (err)
-		return err;
+		goto unlock;
 
 	err = mv88e6xxx_port_commit_pvid(chip, port);
 	if (err)