bonding: remove NULL verification from bond_get_bond_by_slave()

Every caller relies on the result being the actual bond, so this
verification just masks the real problem.

CC: Jay Vosburgh <j.vosburgh@gmail.com>
CC: Andy Gospodarek <andy@greyhouse.net>
Signed-off-by: NVeaceslav Falico <vfalico@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/bonding/bonding.h

@@ -249,8 +249,6 @@ static inline struct slave *bond_get_slave_by_dev(struct bonding *bond,
 
 static inline struct bonding *bond_get_bond_by_slave(struct slave *slave)
 {
-	if (!slave || !slave->bond)
-		return NULL;
 	return slave->bond;
 }