net: sched: act_ipt: get rid of tcf_ipt_walker/tcf_xt_walker and tcf_ipt_search/tcf_xt_search

tcf_ipt_walker()/tcf_xt_walker() and tcf_ipt_search()/tcf_xt_search() do
the same thing as generic walk/search function, so remove them.

Signed-off-by: Zhengchao Shao <shaozhengchao@huawei.com>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>