net_sched: use explicit size of struct tcmsg, remove need to declare tcm

Pointer tcm is being initialized and is never read, it is only being used
to determine the size of struct tcmsg.  Clean this up by removing
variable tcm and explicitly using the sizeof struct tcmsg rather than *tcm.
Cleans up clang warning:

warning: Value stored to 'tcm' during its initialization is never read
Signed-off-by: NColin Ian King <colin.king@canonical.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/sched/sch_api.c

@@ -1500,7 +1500,6 @@ static int tc_dump_qdisc(struct sk_buff *skb, struct netlink_callback *cb)
 	int s_idx, s_q_idx;
 	struct net_device *dev;
 	const struct nlmsghdr *nlh = cb->nlh;
-	struct tcmsg *tcm = nlmsg_data(nlh);
 	struct nlattr *tca[TCA_MAX + 1];
 	int err;
 
@@ -1510,7 +1509,7 @@ static int tc_dump_qdisc(struct sk_buff *skb, struct netlink_callback *cb)
 	idx = 0;
 	ASSERT_RTNL();
 
-	err = nlmsg_parse(nlh, sizeof(*tcm), tca, TCA_MAX, NULL, NULL);
+	err = nlmsg_parse(nlh, sizeof(struct tcmsg), tca, TCA_MAX, NULL, NULL);
 	if (err < 0)
 		return err;