bonding: remove unwanted lock for bond_option_active_slave_set()

The bond_option_active_slave_set() is always called in RTNL,
the RTNL could protect bond slave list, so remove the unwanted
bond lock.

Suggested-by: Jay Vosburgh <fubar@us.ibm.com>
Suggested-by: Veaceslav Falico <vfalico@redhat.com>
Signed-off-by: Ding Tianhong <dingtianhong@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/bonding/bond_options.c

@@ -107,7 +107,6 @@ int bond_option_active_slave_set(struct bonding *bond,
 	}
 
 	block_netpoll_tx();
-	read_lock(&bond->lock);
 	write_lock_bh(&bond->curr_slave_lock);
 
 	/* check to see if we are clearing active */
@@ -142,7 +141,6 @@ int bond_option_active_slave_set(struct bonding *bond,
 	}
 
 	write_unlock_bh(&bond->curr_slave_lock);
-	read_unlock(&bond->lock);
 	unblock_netpoll_tx();
 	return ret;
 }