net: mvpp2: fix maybe-uninitialized warning

This is to fix the following maybe-uninitialized warning:

drivers/net/ethernet/marvell/mvpp2.c:6007:18: warning: 'err' may be
used uninitialized in this function [-Wmaybe-uninitialized]
Signed-off-by: Jisheng Zhang <jszhang@marvell.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/marvell/mvpp2.c

@@ -6047,8 +6047,10 @@ static int mvpp2_port_init(struct mvpp2_port *port)
 
 		/* Map physical Rx queue to port's logical Rx queue */
 		rxq = devm_kzalloc(dev, sizeof(*rxq), GFP_KERNEL);
-		if (!rxq)
+		if (!rxq) {
+			err = -ENOMEM;
 			goto err_free_percpu;
+		}
 		/* Map this Rx queue to a physical queue */
 		rxq->id = port->first_rxq + queue;
 		rxq->port = port->id;