iwlwifi: mvm: fix assert 0x2B00 on older FWs

We should add the multicast station before adding the
broadcast station.

However, in older FW, the firmware will start beaconing
when we add the multicast station, and since the broadcast
station is not added at this point so the transmission
of the beacon will fail on assert 0x2b00.

This is fixed in later firmware, so make the order
of addition depend on the TLV.

Fixes: 26d6c16b ("iwlwifi: mvm: add multicast station")
Signed-off-by: Sara Sharon <sara.sharon@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>