net: sched: act_connmark: get rid of tcf_connmark_walker and tcf_connmark_search

tcf_connmark_walker() and tcf_connmark_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>