stmmac: fix changing mac address

Without the IFF_LIVE_ADDR_CHANGE flag being set, the network code
disallows changing the mac address while the interface is UP.

Consequences are, for instance, that the interface can't be used
in a failover bond.

Add the missing flag to net_device priv_flags.

Tested on Intel Elkhart Lake with default settings, as well as with
failover and alb mode bonds.
Signed-off-by: Corinna Vinschen <vinschen@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

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

@@ -7339,6 +7339,8 @@ int stmmac_dvr_probe(struct device *device,
 	if (flow_ctrl)
 		priv->flow_ctrl = FLOW_AUTO;	/* RX/TX pause on */
 
+	ndev->priv_flags |= IFF_LIVE_ADDR_CHANGE;
+
 	/* Setup channels NAPI */
 	stmmac_napi_add(ndev);