iwlwifi: mvm: support MONITOR vif in DQA mode

In DQA mode the TXQs are allocated on demand, so make
sure the sniffer STA tfd_queue_msk isn't set.

Signed-off-by: Liad Kaufman <liad.kaufman@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>