sctp: Use skb_queue_is_first().

Instead of direct skb_queue_head pointer accesses.

Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/sctp/ulpqueue.c b/net/sctp/ulpqueue.c
index 0b42710..331cc73 100644
--- a/net/sctp/ulpqueue.c
+++ b/net/sctp/ulpqueue.c
@@ -459,7 +459,7 @@
 			 * element in the queue, then count it towards
 			 * possible PD.
 			 */
-			if (pos == ulpq->reasm.next) {
+			if (skb_queue_is_first(&ulpq->reasm, pos)) {
 			    pd_first = pos;
 			    pd_last = pos;
 			    pd_len = pos->len;