iwlwifi: mvm: stop static queues correctly

iwlwifi: mvm: stop static queues correctly

AP interfaces still use some static TX queues (for probes,
broadcast and multicast frames). These queues were not stopped
correctly when the transport layer indicated the queue should be
stopped. As a result, when flushing the queues, new frames from
the overflow queue were tx'd, so the queues still had frames after
flushing. This ended up in an assert since trying to remove a station
with non-empty queues.

Fix it by stopping the static queues correctly when required.

Signed-off-by: Avraham Stern <avraham.stern@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>