iwlwifi: mvm: really disable TDLS queues

for_each_set_bit expect the size in number of bits and not
in bytes.

Fixes: a0f6bf2a ("iwlwifi: mvm: use private TFD queues for TDLS stations")
Reviewed-by: Arik Nemtsov <arik@wizery.com>
Reviewed-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>