[BRIDGE]: Fix faulty check in br_stp_recalculate_bridge_id()

One of the conversions from memcmp to compare_ether_addr is incorrect.
We need to do relative comparison to determine min MAC address to
use in bridge id. 
Signed-off-by: Stephen Hemminger <shemminger@osdl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/bridge/br_stp_if.c

@@ -157,7 +157,7 @@ void br_stp_recalculate_bridge_id(struct net_bridge *br)
 
 	list_for_each_entry(p, &br->port_list, list) {
 		if (addr == br_mac_zero ||
-		    compare_ether_addr(p->dev->dev_addr, addr) < 0)
+		    memcmp(p->dev->dev_addr, addr, ETH_ALEN) < 0)
 			addr = p->dev->dev_addr;
 
 	}