iwlwifi: mvm: Allow TKIP for AP mode

Support for setting keys for TKIP cipher suite was mistakenly removed
for AP mode. Fix this.

Fixes: 85aeb58c ("iwlwifi: mvm: Enable security on new TX API")
Signed-off-by: Ilan Peer <ilan.peer@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>