net: hns3: check NULL pointer before use

This patch checks ops->set_default_reset_request whether is NULL
before using it in function hns3_slot_reset.
Signed-off-by: NGuangbin Huang <huangguangbin2@huawei.com>
Signed-off-by: NHuazhong Tan <tanhuazhong@huawei.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

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

@@ -2006,7 +2006,8 @@ static pci_ers_result_t hns3_slot_reset(struct pci_dev *pdev)
 
 	ops = ae_dev->ops;
 	/* request the reset */
-	if (ops->reset_event && ops->get_reset_level) {
+	if (ops->reset_event && ops->get_reset_level &&
+	    ops->set_default_reset_request) {
 		if (ae_dev->hw_err_reset_req) {
 			reset_type = ops->get_reset_level(ae_dev,
 						&ae_dev->hw_err_reset_req);