net: introduce new priv_flag indicating iface capable of change mac when running

Introduce IFF_LIVE_ADDR_CHANGE priv_flag and use it to disable
netif_running() check in eth_mac_addr()

Signed-off-by: Jiri Pirko <jpirko@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ethernet/eth.c b/net/ethernet/eth.c
index 36e5880..db6a6c1 100644
--- a/net/ethernet/eth.c
+++ b/net/ethernet/eth.c
@@ -283,7 +283,7 @@
 {
 	struct sockaddr *addr = p;
 
-	if (netif_running(dev))
+	if (!(dev->priv_flags & IFF_LIVE_ADDR_CHANGE) && netif_running(dev))
 		return -EBUSY;
 	if (!is_valid_ether_addr(addr->sa_data))
 		return -EADDRNOTAVAIL;