Use kfree_skb() instead of kfree() to free sk_buff.

Fixes: 0d051bf9 ("tipc: make bearer packet filtering generic")
Signed-off-by: NWei Yongjun <weiyongjun1@huawei.com>
Acked-by: NYing Xue <ying.xue@windriver.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>