iwlwifi: manage QoS by mac stack

We activate/deactivate QoS and setup default queue parameters in iwlwifi
driver. Mac stack do the same, so we do not need repeat that work here.
Stack also will tell when disable QoS, this will fix driver when working
with older APs, that do not have QoS implemented.

Patch make "force = true" in iwl_active_qos() assuming we always want
to do with QoS what mac stack wish.

Patch also remove unused qos_cap bits, do not initialize qos_active = 0,
as we have it initialized to zero by kzalloc.

Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>