net: stmmac: add separate warning for PTP not being supported by HW

Chips like Amlogic S905GXBB are supported by this driver but don't
have support for PTP. Add a separate warning for missing HW support
to differentiate it from other actual failures.
Signed-off-by: NHeiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

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

@@ -1726,8 +1726,10 @@ static int stmmac_hw_setup(struct net_device *dev, bool init_ptp)
 
 	if (init_ptp) {
 		ret = stmmac_init_ptp(priv);
-		if (ret)
-			netdev_warn(priv->dev, "fail to init PTP.\n");
+		if (ret == -EOPNOTSUPP)
+			netdev_warn(priv->dev, "PTP not supported by HW\n");
+		else if (ret)
+			netdev_warn(priv->dev, "PTP init failed\n");
 	}
 
 #ifdef CONFIG_DEBUG_FS