Fix access illegal address problem in following condition:

There are multiple devfreq cooling devices in system, some of them has
EM model but others do not. Energy model ops such as state2power will
append to global devfreq_cooling_ops when the cooling device with
EM model is registered. It makes the cooling device without EM model
also use devfreq_cooling_ops after appending when registered later by
of_devfreq_cooling_register_power() or of_devfreq_cooling_register().

The IPA governor regards the cooling devices without EM model as a power
actor, because they also have energy model ops, and will access illegal
address at dfc->em_pd when execute cdev->ops->get_requested_power,
cdev->ops->state2power or cdev->ops->power2state.

Fixes: 615510fe ("thermal: devfreq_cooling: remove old power model and use EM")
Cc: 5.13+ <stable@vger.kernel.org> # 5.13+
Signed-off-by: Kant Fan <kant@allwinnertech.com>
Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>