iwlwifi: hard code power save mode to CAM for 22560 devices

Balanced power save mode isn't supported in the fw for 22560 devices
yet.  Configure the power save mode to CAM until it gets implemented.

Signed-off-by: Golan Ben Ami <golan.ben.ami@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>