bonding: slight optimization for bond_3ad_xmit_xor()

The bond_dev_queue_xmit() will always return 0, and as a fast path,
it is inappropriate to check the res value when xmit every package,
so remove the res check and avoid once judgement for xmit.

Signed-off-by: Ding Tianhong <dingtianhong@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>