bonding: reread information about speed and duplex when interface goes up

When an interface was enslaved when it was down, bonding thinks
it has speed -1 even after it goes up. This leads into selecting
a wrong active interface in active/backup mode on mixed 10G/1G or
1G/100M environment.

before:
 bonding: bond0: link status definitely up for interface eth5, 100 Mbps full duplex.
 bonding: bond0: link status definitely up for interface eth0, 100 Mbps full duplex.

after:
 bonding: bond0: link status definitely up for interface eth5, 10000 Mbps full duplex.
 bonding: bond0: link status definitely up for interface eth0, 1000 Mbps full duplex.

Signed-off-by: Krzysztof Piotr Oledzki <ole@ans.pl>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/bonding/bond_main.c

@@ -2406,6 +2406,8 @@ static void bond_miimon_commit(struct bonding *bond)
 				slave->state = BOND_STATE_BACKUP;
 			}
 
+			bond_update_speed_duplex(slave);
+
 			pr_info("%s: link status definitely up for interface %s, %d Mbps %s duplex.\n",
 				bond->dev->name, slave->dev->name,
 				slave->speed, slave->duplex ? "full" : "half");