mm: Replace deprecated CPU-hotplug functions.

The functions get_online_cpus() and put_online_cpus() have been
deprecated during the CPU hotplug rework. They map directly to
cpus_read_lock() and cpus_read_unlock().

Replace deprecated CPU-hotplug functions with the official version.
The behavior remains unchanged.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20210803141621.780504-21-bigeasy@linutronix.de

diff --git a/mm/swap_slots.c b/mm/swap_slots.c
index a66f3e0..16f706c 100644
--- a/mm/swap_slots.c
+++ b/mm/swap_slots.c
@@ -70,9 +70,9 @@ void disable_swap_slots_cache_lock(void)
 	swap_slot_cache_enabled = false;
 	if (swap_slot_cache_initialized) {
 		/* serialize with cpu hotplug operations */
-		get_online_cpus();
+		cpus_read_lock();
 		__drain_swap_slots_cache(SLOTS_CACHE|SLOTS_CACHE_RET);
-		put_online_cpus();
+		cpus_read_unlock();
 	}
 }