iwlwifi: mvm: enable dynamic queue allocation mode

New firmwares support dynamic queue allocation (DQA), which enables
on-demand allocation of queues per RA/TID, instead of allocating them
statically per vif.  This allows an AP to send, for instance, BE
traffic to STA2 even if it also needs to send traffic to a sleeping
STA1, without being blocked by the sleeping station.

The implementation in the driver is now ready, so we can enable this
feature by default when running firmwares that support it.

Signed-off-by: Liad Kaufman <liad.kaufman@intel.com>
[reworded the commit message]
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>