ipq40xx: abort ar40xx probe on missing PHYs

The ar40xx driver currently panics in case no QCA807x PHY has been
successfully probed. This happens when the external PHY is still
in reset when probing the ar40xx switch driver.

Note that this patch does not fix the root cause, ar40xx_probe now
simply fails instead of causing a kernel panic due to a nullpointer
dereference.

Signed-off-by: David Bauer <mail@david-bauer.net>
(cherry picked from commit e2c084cabc2b2a2fffc36aee3e48874f9862c74a)

target/linux/ipq40xx/patches-4.14/706-ar40xx-abort-probe-on-missig-phy.patch

@@ -0,0 +1,23 @@
+--- a/drivers/net/phy/ar40xx.c
++++ b/drivers/net/phy/ar40xx.c
+@@ -2021,6 +2021,12 @@ static int ar40xx_probe(struct platform_
+ 	/* register switch */
+ 	swdev = &priv->dev;
+ 
++	if (priv->mii_bus == NULL) {
++		dev_err(&pdev->dev, "Probe failed - Missing PHYs!\n");
++		ret = -ENODEV;
++		goto err_missing_phy;
++	}
++
+ 	swdev->alias = dev_name(&priv->mii_bus->dev);
+ 
+ 	swdev->cpu_port = AR40XX_PORT_CPU;
+@@ -2052,6 +2058,7 @@ err_unregister_switch:
+ 	unregister_switch(&priv->dev);
+ err_unregister_phy:
+ 	phy_driver_unregister(&ar40xx_phy_driver);
++err_missing_phy:
+ 	platform_set_drvdata(pdev, NULL);
+ 	return ret;
+ }