net: stmmac: Fix VLAN filter delete timeout issue in Intel mGBE SGMII

For Intel mGbE controller, MAC VLAN filter delete operation will time-out
if serdes power-down sequence happened first during driver remove() with
below message.

[82294.764958] intel-eth-pci 0000:00:1e.4 eth2: stmmac_dvr_remove: removing driver
[82294.778677] intel-eth-pci 0000:00:1e.4 eth2: Timeout accessing MAC_VLAN_Tag_Filter
[82294.779997] intel-eth-pci 0000:00:1e.4 eth2: failed to kill vid 0081/0
[82294.947053] intel-eth-pci 0000:00:1d.2 eth1: stmmac_dvr_remove: removing driver
[82295.002091] intel-eth-pci 0000:00:1d.1 eth0: stmmac_dvr_remove: removing driver

Therefore, we delay the serdes power-down to be after unregister_netdev()
which triggers the VLAN filter delete.

Fixes: b9663b7c ("net: stmmac: Enable SERDES power up/down sequence")
Signed-off-by: Ong Boon Leong <boon.leong.ong@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

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

@@ -5249,13 +5249,16 @@ int stmmac_dvr_remove(struct device *dev)
 	netdev_info(priv->dev, "%s: removing driver", __func__);
 
 	stmmac_stop_all_dma(priv);
+	stmmac_mac_set(priv, priv->ioaddr, false);
+	netif_carrier_off(ndev);
+	unregister_netdev(ndev);
 
+	/* Serdes power down needs to happen after VLAN filter
+	 * is deleted that is triggered by unregister_netdev().
+	 */
 	if (priv->plat->serdes_powerdown)
 		priv->plat->serdes_powerdown(ndev, priv->plat->bsp_priv);
 
-	stmmac_mac_set(priv, priv->ioaddr, false);
-	netif_carrier_off(ndev);
-	unregister_netdev(ndev);
 #ifdef CONFIG_DEBUG_FS
 	stmmac_exit_fs(ndev);
 #endif