iwlwifi: mvm: Don't install CMAC/GMAC key in AP mode

iwlwifi: mvm: Don't install CMAC/GMAC key in AP mode

Due to a missing break, the management multicast key was installed even
though we don't really support it. Fix that, so mac80211 would know that
it should protect frames in software.

Signed-off-by: Andrei Otcheretianski <andrei.otcheretianski@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Link: https://lore.kernel.org/r/iwlwifi.20200926002540.019a64e96d44.I609a995611ac5286e442cd54f764eaf4a7249ac0@changeid
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>