iwlwifi: mvm: set the MFP flag for keys that are used by MFP stations

22000 devices rely on this flag to install the key to the right
queues.  For earlier devices we didn't have a key / queue mapping and
the key was sent along with the Tx command for each Tx hence the
problem didn't arise.

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