iwlwifi: mvm: map cab_queue to different txq_id

cab_queue can now get bigger than u8, since in TVQM we will support
512 queues..
Support it by maintaining internal mapping between the actual number
and mac80211 queue (IWL_MVM_DQA_GCAST_QUEUE).
For pre-a000 the internal queue will be the same as the mac80211
queue.

Signed-off-by: Sara Sharon <sara.sharon@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>