net: ar8216: prevent device duplication in ar8xxx_dev_list

Import from fd7b89dd46%5E%21/#F0
Signed-off-by: Pavel Kubelun <be.dissent@gmail.com>

CHROMIUM: drivers: ar8216: prevent device duplication in ar8xxx_dev_list

If probe is called twice, once for PHY0 and a second time for PHY4,
the same switch device will be added twice to ar8xxx_dev_list, while
supposedly this list should have one element per hardware switch present
in the system.

While no negative impact have been observed, it does happen if a
platform instanciates these two PHYs from device-tree, as an example.

Change-Id: Iddcbdf7d4adacb0af01975b73f8e56b4582e894e
Signed-off-by: Mathieu Olivari <mathieu@codeaurora.org>
Reviewed-on: https://chromium-review.googlesource.com/234790
Reviewed-by: Matthias Kaehlcke <mka@chromium.org>
Reviewed-by: Toshi Kikuchi <toshik@chromium.org>
Tested-by: Toshi Kikuchi <toshik@chromium.org>

target/linux/generic/files/drivers/net/phy/ar8216.c

@@ -2171,6 +2171,8 @@ ar8xxx_phy_probe(struct phy_device *phydev)
 		swdev->devname, swdev->name, priv->chip_rev,
 		dev_name(&priv->mii_bus->dev));
 
+	list_add(&priv->list, &ar8xxx_dev_list);
+
 found:
 	priv->use_count++;
 
@@ -2199,8 +2201,6 @@ found:
 
 	phydev->priv = priv;
 
-	list_add(&priv->list, &ar8xxx_dev_list);
-
 	mutex_unlock(&ar8xxx_dev_list_lock);
 
 	return 0;