net: stmmac: use SPEED_UNKNOWN/DUPLEX_UNKNOWN

It is better to use DUPLEX_UNKNOWN instead of just "-1".
Using 0 for an invalid speed is bad since 0 is a valid value for speed.
So this patch replace 0 by SPEED_UNKNOWN.
Signed-off-by: Corentin Labbe <clabbe.montjoie@gmail.com>
Acked-by: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Reviewed-by: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

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

@@ -754,8 +754,8 @@ static void stmmac_adjust_link(struct net_device *dev)
 	} else if (priv->oldlink) {
 		new_state = 1;
 		priv->oldlink = 0;
-		priv->speed = 0;
-		priv->oldduplex = -1;
+		priv->speed = SPEED_UNKNOWN;
+		priv->oldduplex = DUPLEX_UNKNOWN;
 	}
 
 	if (new_state && netif_msg_link(priv))
@@ -817,8 +817,8 @@ static int stmmac_init_phy(struct net_device *dev)
 	int interface = priv->plat->interface;
 	int max_speed = priv->plat->max_speed;
 	priv->oldlink = 0;
-	priv->speed = 0;
-	priv->oldduplex = -1;
+	priv->speed = SPEED_UNKNOWN;
+	priv->oldduplex = DUPLEX_UNKNOWN;
 
 	if (priv->plat->phy_node) {
 		phydev = of_phy_connect(dev, priv->plat->phy_node,
@@ -3434,8 +3434,8 @@ int stmmac_suspend(struct device *dev)
 	spin_unlock_irqrestore(&priv->lock, flags);
 
 	priv->oldlink = 0;
-	priv->speed = 0;
-	priv->oldduplex = -1;
+	priv->speed = SPEED_UNKNOWN;
+	priv->oldduplex = DUPLEX_UNKNOWN;
 	return 0;
 }
 EXPORT_SYMBOL_GPL(stmmac_suspend);