[DCCP]: Tidyup CCID3 list handling

As Arnaldo Carvalho de Melo points out I should be using list_entry in case
the structure changes in future. Current code functions but is reliant
on position and requires type cast.

Noticed when doing this that I have one more variable than I needed so
removing that also.

Signed off by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/dccp/ccids/ccid3.c

@@ -900,23 +900,23 @@ static u32 ccid3_hc_rx_calc_first_li(struct sock *sk)
 static void ccid3_hc_rx_update_li(struct sock *sk, u64 seq_loss, u8 win_loss)
 {
 	struct ccid3_hc_rx_sock *hcrx = ccid3_hc_rx_sk(sk);
-	struct dccp_li_hist_entry *next, *head;
+	struct dccp_li_hist_entry *head;
 	u64 seq_temp;
 
 	if (list_empty(&hcrx->ccid3hcrx_li_hist)) {
 		if (!dccp_li_hist_interval_new(ccid3_li_hist,
 		   &hcrx->ccid3hcrx_li_hist, seq_loss, win_loss))
 			return;
 
-		next = (struct dccp_li_hist_entry *)
-		   hcrx->ccid3hcrx_li_hist.next;
-		next->dccplih_interval = ccid3_hc_rx_calc_first_li(sk);
+		head = list_entry(hcrx->ccid3hcrx_li_hist.next,
+		   struct dccp_li_hist_entry, dccplih_node);
+		head->dccplih_interval = ccid3_hc_rx_calc_first_li(sk);
 	} else {
 		struct dccp_li_hist_entry *entry;
 		struct list_head *tail;
 
-		head = (struct dccp_li_hist_entry *)
-		   hcrx->ccid3hcrx_li_hist.next;
+		head = list_entry(hcrx->ccid3hcrx_li_hist.next,
+		   struct dccp_li_hist_entry, dccplih_node);
 		/* FIXME win count check removed as was wrong */
 		/* should make this check with receive history */
 		/* and compare there as per section 10.2 of RFC4342 */