bonding: remove the unused macro

Cc: Jay Vosburgh <j.vosburgh@gmail.com>
Cc: Veaceslav Falico <vfalico@gmail.com>
Cc: Andy Gospodarek <andy@greyhouse.net>
Signed-off-by: NDing Tianhong <dingtianhong@huawei.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/bonding/bonding.h

@@ -183,8 +183,6 @@ struct bond_parm_tbl {
 	int mode;
 };
 
-#define BOND_MAX_MODENAME_LEN 20
-
 struct slave {
 	struct net_device *dev; /* first - useful for panic debug */
 	struct bonding *bond; /* our master */