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

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

Since commit a8bb74acd8efe ("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>