hulk inclusion
category: bugfix
bugzilla: 26326
CVE: NA

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Introduce boolean function system_in_hibernation() returning
'true' when the system carrying out hibernation.

Some device drivers or syscore need such a function to check
if it is in the phase of hibernation.
Signed-off-by: NHongbo Yao <yaohongbo@huawei.com>
Reviewed-by: NHanjun Guo <guohanjun@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>