MINOR: sched: split tasklet_wakeup() into tasklet_wakeup_on()

tasklet_wakeup() only checks tl->tid to know whether the task is
programmed to run on the current thread or on a specific thread. We'll
have to ease this selection in a subsequent patch, preferably without
modifying tl->tid, so let's have a new tasklet_wakeup_on() function
to specify the thread number to run on. That the logic has not changed
at all.
diff --git a/include/haproxy/task.h b/include/haproxy/task.h
index 1f31a76..db91991 100644
--- a/include/haproxy/task.h
+++ b/include/haproxy/task.h
@@ -322,9 +322,12 @@
 	return t;
 }
 
-static inline void tasklet_wakeup(struct tasklet *tl)
+/* schedules tasklet <tl> to run onto thread <thr> or the current thread if
+ * <thr> is negative.
+ */
+static inline void tasklet_wakeup_on(struct tasklet *tl, int thr)
 {
-	if (likely(tl->tid < 0)) {
+	if (likely(thr < 0)) {
 		/* this tasklet runs on the caller thread */
 		if (LIST_ISEMPTY(&tl->list)) {
 			if (tl->state & TASK_SELF_WAKING) {
@@ -349,15 +352,22 @@
 		}
 	} else {
 		/* this tasklet runs on a specific thread */
-		if (MT_LIST_ADDQ(&task_per_thread[tl->tid].shared_tasklet_list, (struct mt_list *)&tl->list) == 1) {
+		if (MT_LIST_ADDQ(&task_per_thread[thr].shared_tasklet_list, (struct mt_list *)&tl->list) == 1) {
 			_HA_ATOMIC_ADD(&tasks_run_queue, 1);
-			if (sleeping_thread_mask & (1UL << tl->tid)) {
-				_HA_ATOMIC_AND(&sleeping_thread_mask, ~(1UL << tl->tid));
-				wake_thread(tl->tid);
+			if (sleeping_thread_mask & (1UL << thr)) {
+				_HA_ATOMIC_AND(&sleeping_thread_mask, ~(1UL << thr));
+				wake_thread(thr);
 			}
 		}
 	}
+}
 
+/* schedules tasklet <tl> to run onto the thread designated by tl->tid, which
+ * is either its owner thread if >= 0 or the current thread if < 0.
+ */
+static inline void tasklet_wakeup(struct tasklet *tl)
+{
+	tasklet_wakeup_on(tl, tl->tid);
 }
 
 /* Insert a tasklet into the tasklet list. If used with a plain task instead,