iwlwifi: mvm: add registration to cooling device

Register cooling device in order to have the Thermal
Manager handle the device's power budget according to the sent
notifications.
The interface adds a new thermal cooling device to
/sys/class/thermal/ folder.

Signed-off-by: Chaya Rachel Ivgi <chaya.rachel.ivgi@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>