MINOR: task: Fix compiler warning.

Waking up task, when checking if it is a valid entry.
Similarly to commit caa8a37ffe5922efda7fd7b882e96964b40d7135,
casting explicitally to void pointer as HA_ATOMIC_CAS needs.
diff --git a/src/task.c b/src/task.c
index fb48407..16c7232 100644
--- a/src/task.c
+++ b/src/task.c
@@ -79,7 +79,7 @@
 	 * in the meanwhile.
 	 */
 redo:
-	if (unlikely(!HA_ATOMIC_CAS(&t->rq.node.leaf_p, &expected, 0x1))) {
+	if (unlikely(!HA_ATOMIC_CAS(&t->rq.node.leaf_p, &expected, (void *)0x1))) {
 		if (root == &rqueue)
 			HA_SPIN_UNLOCK(TASK_RQ_LOCK, &rq_lock);
 		return;