iwlwifi: trans: make aggregation explicit for TX queue handling

Currently a valid sta_id is assumed to mean that the queue is
meant to also be aggregated, but that assumption will not be
true in the future, so don't make it in the lower level but
only in the inline wrapper.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>