rcu-tasks: Convert rcu_tasks_wait_gp() for-loop to while-loop

The infinite for-loop in rcu_tasks_wait_gp() has its only exit at the
top of the loop, so this commit does the straightforward conversion to
a while-loop, thus saving a few lines.
Signed-off-by: NPaul E. McKenney <paulmck@kernel.org>

kernel/rcu/tasks.h

@@ -338,14 +338,11 @@ static void rcu_tasks_wait_gp(struct rcu_tasks *rtp)
 	if (fract > HZ)
 		fract = HZ;
 
-	for (;;) {
+	while (!list_empty(&holdouts)) {
 		bool firstreport;
 		bool needreport;
 		int rtst;
 
-		if (list_empty(&holdouts))
-			break;
-
 		/* Slowly back off waiting for holdouts */
 		set_tasks_gp_state(rtp, RTGS_WAIT_SCAN_HOLDOUTS);
 		schedule_timeout_idle(HZ/fract);