net: dsa: ocelot: unlock on error in vsc9959_qos_port_tas_set()

This error path needs call mutex_unlock(&ocelot->tas_lock) before
returning.

Fixes: 2d800bc ("net/sched: taprio: replace tc_taprio_qopt_offload :: enable with a "cmd" enum")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/dsa/ocelot/felix_vsc9959.c

@@ -1424,7 +1424,8 @@ static int vsc9959_qos_port_tas_set(struct ocelot *ocelot, int port,
 		mutex_unlock(&ocelot->tas_lock);
 		return 0;
 	} else if (taprio->cmd != TAPRIO_CMD_REPLACE) {
-		return -EOPNOTSUPP;
+		ret = -EOPNOTSUPP;
+		goto err_unlock;
 	}
 
 	ret = ocelot_port_mqprio(ocelot, port, &taprio->mqprio);