net: hns3: add netdev reset check for hns3_set_tunable()

When pci device reset failed, it does uninit operation and priv->ring
is NULL, it causes accessing NULL pointer error.

Add netdev reset check for hns3_set_tunable() to fix it.

Fixes: 99f6b5fb ("net: hns3: use bounce buffer when rx page can not be reused")
Signed-off-by: Hao Chen <chenhao288@hisilicon.com>
Signed-off-by: Guangbin Huang <huangguangbin2@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/hisilicon/hns3/hns3_ethtool.c

@@ -1766,9 +1766,6 @@ static int hns3_set_tx_spare_buf_size(struct net_device *netdev,
 	struct hnae3_handle *h = priv->ae_handle;
 	int ret;
 
-	if (hns3_nic_resetting(netdev))
-		return -EBUSY;
-
 	h->kinfo.tx_spare_buf_size = data;
 
 	ret = hns3_reset_notify(h, HNAE3_DOWN_CLIENT);
@@ -1799,6 +1796,11 @@ static int hns3_set_tunable(struct net_device *netdev,
 	struct hnae3_handle *h = priv->ae_handle;
 	int i, ret = 0;
 
+	if (hns3_nic_resetting(netdev) || !priv->ring) {
+		netdev_err(netdev, "failed to set tunable value, dev resetting!");
+		return -EBUSY;
+	}
+
 	switch (tuna->id) {
 	case ETHTOOL_TX_COPYBREAK:
 		priv->tx_copybreak = *(u32 *)data;