net: hns3: fix a phy loopback fail issue

When phy driver does not implement the set_loopback interface,
phy loopback test will return -EOPNOTSUPP, and the loopback test
will fail. So when phy driver does not implement the set_loopback
interface, don't do phy loopback test.

Fixes: c9765a89 ("net: hns3: add phy selftest function")
Signed-off-by: Yonglong Liu <liuyonglong@huawei.com>
Signed-off-by: Huazhong Tan <tanhuazhong@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/hisilicon/hns3/hns3pf/hclge_main.c

@@ -752,7 +752,8 @@ static int hclge_get_sset_count(struct hnae3_handle *handle, int stringset)
 		handle->flags |= HNAE3_SUPPORT_SERDES_SERIAL_LOOPBACK;
 		handle->flags |= HNAE3_SUPPORT_SERDES_PARALLEL_LOOPBACK;
 
-		if (hdev->hw.mac.phydev) {
+		if (hdev->hw.mac.phydev && hdev->hw.mac.phydev->drv &&
+		    hdev->hw.mac.phydev->drv->set_loopback) {
 			count += 1;
 			handle->flags |= HNAE3_SUPPORT_PHY_LOOPBACK;
 		}