iwlwifi: mvm: Add PBW snoozing enablement

The Performance Based Window snooze mechanism is based on uAPSD and is
used in low-medium traffic scenarios, in order to provide better power
performance while insuring low latency and jitter for the incoming traffic.
This patch enables PBW snoozing in case uAPSD is enabled and all ACs are
uAPSD trigger and delivery enabled.

Signed-off-by: Alexander Bondar <alexander.bondar@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>