net: hns3: do not initialize mdio bus when phy is inexistent

driver inclusion
category: bugfix
bugzilla: NA
CVE: NA

For some boards, phy is not connected to mdio bus. In this case,
mdio bus initialization will fail, then cause the device initialize
fail.

This patch fixes it by skip the mdio bus initialization when phy
is inexistent.
Signed-off-by: Nshenjian (K) <shenjian15@huawei.com>
Reviewed-by: Nlipeng <lipeng321@huawei.com>
Reviewed-by: NHanjun Guo <guohanjun@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

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

@@ -111,12 +111,18 @@ static int hclge_mdio_read(struct mii_bus *bus, int phyid, int regnum)
 
 int hclge_mac_mdio_config(struct hclge_dev *hdev)
 {
+#define PHY_INEXISTENT	255
+
 	struct hclge_mac *mac = &hdev->hw.mac;
 	struct phy_device *phydev;
 	struct mii_bus *mdio_bus;
 	int ret;
 
-	if (hdev->hw.mac.phy_addr >= PHY_MAX_ADDR) {
+	if (hdev->hw.mac.phy_addr == PHY_INEXISTENT) {
+		dev_info(&hdev->pdev->dev,
+			 "no phy device is connected to mdio bus\n");
+		return 0;
+	} else if (hdev->hw.mac.phy_addr >= PHY_MAX_ADDR) {
 		dev_err(&hdev->pdev->dev, "phy_addr(%d) is too large.\n",
 			hdev->hw.mac.phy_addr);
 		return -EINVAL;