net_sched: move tc_action into tcf_common

struct tc_action is confusing, currently we use it for two purposes:
1) Pass in arguments and carry out results from helper functions
2) A generic representation for tc actions

The first one is error-prone, since we need to make sure we don't
miss anything. This patch aims to get rid of this use, by moving
tc_action into tcf_common, so that they are allocated together
in hashtable and can be cast'ed easily.

And together with the following patch, we could really make
tc_action a generic representation for all tc actions and each
type of action can inherit from it.

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

include/net/tc_act/tc_csum.h

@@ -9,7 +9,6 @@ struct tcf_csum {
 
 	u32 update_flags;
 };
-#define to_tcf_csum(a) \
-	container_of(a->priv,struct tcf_csum,common)
+#define to_tcf_csum(a) ((struct tcf_csum *)a)
 
 #endif /* __NET_TC_CSUM_H */