iwlwifi: mvm: use the new session protection command

The firmware has now a new session protection command.
This new API allows the firmware to manage the protection
needed for association. It'll also remove the event when
the association is complete.

Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>