net: usb: asix: Fix less than zero comparison of a u16

The comparison of the u16 priv->phy_addr < 0 is always false because
phy_addr is unsigned. Fix this by assigning the return from the call
to function asix_read_phy_addr to int ret and using this for the
less than zero error check comparison.

Addresses-Coverity: ("Unsigned compared against 0")
Fixes: e532a096 ("net: usb: asix: ax88772: add phylib support")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/usb/asix_devices.c

@@ -704,9 +704,11 @@ static int ax88772_init_phy(struct usbnet *dev)
 	struct asix_common_private *priv = dev->driver_priv;
 	int ret;
 
-	priv->phy_addr = asix_read_phy_addr(dev, true);
-	if (priv->phy_addr < 0)
-		return priv->phy_addr;
+	ret = asix_read_phy_addr(dev, true);
+	if (ret < 0)
+		return ret;
+
+	priv->phy_addr = ret;
 
 	snprintf(priv->phy_name, sizeof(priv->phy_name), PHY_ID_FMT,
 		 priv->mdio->id, priv->phy_addr);