ACPI: APEI: Remove redundant rcu_read_lock/unlock() under spinlock

Since commit a8bb74a ("rcu: Consolidate RCU-sched update-side
function definitions") there is no difference between rcu_read_lock(),
rcu_read_lock_bh() and rcu_read_lock_sched() in terms of RCU read
section and the relevant grace period. That means that spin_lock(),
which implies rcu_read_lock_sched(), also implies rcu_read_lock().

There is no need no explicitly start a RCU read section if one has
already been started implicitly by spin_lock().

Simplify the code and remove the inner rcu_read_lock() invocation.

Signed-off-by: pengdonglin <pengdonglin@xiaomi.com>
Signed-off-by: pengdonglin <dolinux.peng@gmail.com>
Reviewed-by: Hanjun Guo <guohanjun@huawei.com>
Link: https://patch.msgid.link/20250916044735.2316171-2-dolinux.peng@gmail.com
[ rjw: Subject adjustment ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Author: pengdonglin

drivers/acpi/apei/ghes.c

@@ -1207,12 +1207,10 @@ static int ghes_notify_hed(struct notifier_block *this, unsigned long event,
 	int ret = NOTIFY_DONE;
 
 	spin_lock_irqsave(&ghes_notify_lock_irq, flags);
-	rcu_read_lock();
 	list_for_each_entry_rcu(ghes, &ghes_hed, list) {
 		if (!ghes_proc(ghes))
 			ret = NOTIFY_OK;
 	}
-	rcu_read_unlock();
 	spin_unlock_irqrestore(&ghes_notify_lock_irq, flags);
 
 	return ret;