iwlwifi: mvm: drop low_latency_agg_frame_cnt_limit

This was an old workaround for solving latency issues with
certain Miracast adapters like ActionTec. However this isn't
needed anymore and furthermore it hurts throughput in other
use cases.

Signed-off-by: Eyal Shapira <eyalx.shapira@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>