net: hns3: add a check for get_reset_level

For some cases, ops->get_reset_level may not be implemented, so we
should check whether it is NULL before calling get_reset_level.
Signed-off-by: Guangbin Huang <huangguangbin@huawei.com>
Signed-off-by: Huazhong Tan <tanhuazhong@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/hisilicon/hns3/hns3_enet.c

@@ -1963,7 +1963,7 @@ static pci_ers_result_t hns3_slot_reset(struct pci_dev *pdev)
 
 	ops = ae_dev->ops;
 	/* request the reset */
-	if (ops->reset_event) {
+	if (ops->reset_event && ops->get_reset_level) {
 		if (ae_dev->hw_err_reset_req) {
 			reset_type = ops->get_reset_level(ae_dev,
 						&ae_dev->hw_err_reset_req);