This fixes the following harmless warning:

./ip/ip fou del port 7777
[  122.907516] udp_del_offload: didn't find offload for port 7777

Cc: Tom Herbert <tom@herbertland.com>
Signed-off-by: NCong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>