r8169: fix mac address change

Network core refuses to change mac address because flag
IFF_LIVE_ADDR_CHANGE isn't set. Set this missing flag.

Fixes: 1f7aa2bc ("r8169: simplify rtl_set_mac_address")
Reported-by: NCorinna Vinschen <vinschen@redhat.com>
Signed-off-by: NHeiner Kallweit <hkallweit1@gmail.com>
Tested-by: NCorinna Vinschen <vinschen@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/realtek/r8169.c

@@ -7789,6 +7789,7 @@ static int rtl_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
 		NETIF_F_HW_VLAN_CTAG_RX;
 	dev->vlan_features = NETIF_F_SG | NETIF_F_IP_CSUM | NETIF_F_TSO |
 		NETIF_F_HIGHDMA;
+	dev->priv_flags |= IFF_LIVE_ADDR_CHANGE;
 
 	tp->cp_cmd |= RxChkSum | RxVlan;