ACPI / scan: Send change uevent with offine environmental data

In current design of ACPI container offline, Kernel emits
KOBJ_CHANGE uevent to user space to indidate that the ejection of
the container was triggered by platform. (caa73ea1 patch)

A pure KOBJ_CHANGE uevent is not enough for user space to identify
the purpose. For example, a "udevadm trigger" command can also
be used to emit change event to all udev rules. A udev rule can not
identify that the event is from kernel for offline or from udevadm
for other purpose. Then the offline action in udev rule may also be
triggered by udevadm tool.

So, similar to the change uevent of dock, kernel sends the
KOBJ_CHANGE uevent with a offline environmental data to indicate
purpose. It's useful by udev rule for using ENV{EVENT} filter.

Acked-by: Michal Hocko <mhocko@suse.com>
Tested-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: "Lee, Chun-Yi" <jlee@suse.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>