net: stmmac: mdio: fix incorrect phy address check

max_addr is the max number of addresses, not the highest possible address,
therefore check phydev->mdio.addr > max_addr isn't correct.
To fix this change the semantics of max_addr, so that it represents
the highest possible address. IMO this is also a little bit more intuitive
wrt name max_addr.

Fixes: 4a107a0e8361 ("net: stmmac: mdio: use phy_find_first to simplify stmmac_mdio_register")
Reported-by: Dan Carpenter <[e-mail]>
Reported-by: Simon Horman <[e-mail]>
Signed-off-by: Heiner Kallweit <[e-mail]>
Reviewed-by: Simon Horman <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

drivers/net/ethernet/stmicro/stmmac/stmmac_mdio.c

···
 	struct device_node *mdio_node = priv->plat->mdio_node;
 	struct device *dev = ndev->dev.parent;
 	struct fwnode_handle *fixed_node;
+	int max_addr = PHY_MAX_ADDR - 1;
 	struct fwnode_handle *fwnode;
 	struct phy_device *phydev;
-	int max_addr;
 
 	if (!mdio_bus_data)
 		return 0;
···
 
 		if (priv->synopsys_id < DWXGMAC_CORE_2_20) {
 			/* Right now only C22 phys are supported */
-			max_addr = MII_XGMAC_MAX_C22ADDR + 1;
+			max_addr = MII_XGMAC_MAX_C22ADDR;
 
 			/* Check if DT specified an unsupported phy addr */
 			if (priv->plat->phy_addr > MII_XGMAC_MAX_C22ADDR)
 				dev_err(dev, "Unsupported phy_addr (max=%d)\n",
 					MII_XGMAC_MAX_C22ADDR);
-		} else {
-			/* XGMAC version 2.20 onwards support 32 phy addr */
-			max_addr = PHY_MAX_ADDR;
 		}
 	} else {
 		new_bus->read = &stmmac_mdio_read_c22;
···
 			new_bus->read_c45 = &stmmac_mdio_read_c45;
 			new_bus->write_c45 = &stmmac_mdio_write_c45;
 		}
-
-		max_addr = PHY_MAX_ADDR;
 	}
 
 	if (mdio_bus_data->needs_reset)