After the previous patch, struct tc_action should be enough
to represent the generic tc action, tcf_common is not necessary
any more. This patch gets rid of it to make tc action code
more readable.

Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: NCong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>