iwlwifi: mvm: set the encryption type of an IGTK key

The FW expect the driver to set the encryption algorithm type when
installing the IGTK key in the HW.
Currently when installing CMAC IGTK key we don't set the algorithm type
and as a result the FW fails to calculate the MIC of multicast management
frames.
Fix it.

Signed-off-by: Ayala Beker <ayala.beker@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>