powerpc/mpc83xx: Use wait_event_freezable() for freezable kthread

A freezable kernel thread can enter frozen state during freezing by
either calling try_to_freeze() or using wait_event_freezable() and its
variants. So for the following snippet of code in a kernel thread loop:
  wait_event_interruptible();
  try_to_freeze();

We can change it to a simple wait_event_freezable() and then eliminate
a function call.

Signed-off-by: Kevin Hao <haokexin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20231221044510.1802429-3-haokexin@gmail.com

Author: haokexin

arch/powerpc/platforms/83xx/suspend.c

@@ -264,8 +264,7 @@ static int agent_thread_fn(void *data)
 	set_freezable();
 
 	while (1) {
-		wait_event_interruptible(agent_wq, pci_pm_state >= 2);
-		try_to_freeze();
+		wait_event_freezable(agent_wq, pci_pm_state >= 2);
 
 		if (signal_pending(current) || pci_pm_state < 2)
 			continue;