net: hisilicon: hns: fix error return code of hns_nic_clear_all_rx_fetch()

When hns_assemble_skb() returns NULL to skb, no error return code of
hns_nic_clear_all_rx_fetch() is assigned.
To fix this bug, ret is assigned with -ENOMEM in this case.
Reported-by: TOTE Robot <oslab@tsinghua.edu.cn>
Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/hisilicon/hns/hns_enet.c

@@ -1663,8 +1663,10 @@ static int hns_nic_clear_all_rx_fetch(struct net_device *ndev)
 			for (j = 0; j < fetch_num; j++) {
 				/* alloc one skb and init */
 				skb = hns_assemble_skb(ndev);
-				if (!skb)
+				if (!skb) {
+					ret = -ENOMEM;
 					goto out;
+				}
 				rd = &tx_ring_data(priv, skb->queue_mapping);
 				hns_nic_net_xmit_hw(ndev, skb, rd);