doc: trace: fix reference to cpuidle documentation file

mainline inclusion
from mainline-v5.0-rc2
commit 7604bf09
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I47H3V


CVE: NA

--------------------------------

Old cpuidle/sysfs.txt file was replaced in aa5eee35. So, refer to
an updated file.

Fixes: aa5eee35 (Documentation: admin-guide: PM: Add cpuidle document)
Signed-off-by: Otto Sabart <ottosabart@seberm.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>
Reviewed-by: Xie XiuQi <xiexiuqi@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>