ACPI: battery: Fix possible crash when unregistering a battery hook
In the Linux kernel, the following vulnerability has been resolved:

ACPI: battery: Fix possible crash when unregistering a battery hook

When a battery hook returns an error when adding a new battery, then
the battery hook is automatically unregistered.
However the battery hook provider cannot know that, so it will later
call battery_hook_unregister() on the already unregistered battery
hook, resulting in a crash.

Fix this by using the list head to mark already unregistered battery
hooks as already being unregistered so that they can be ignored by
battery_hook_unregister().