iwlwifi: pcie: get rid of txq id assignment

In TVQM mode the queue ID is assigned after enablement.
Get rid of assuming pre-defined TX queue ID in functions
that will be used by TVQM allocation path.

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