iwlwifi: mvm: Configure fragmented scan for scheduled scan

Configure the FW to use fragmented scan when the traffic load is high
or low latency traffic is on. This is useful for scans that are
managed by the FW (e.g. scheduled scan).

Signed-off-by: Avraham Stern <avraham.stern@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>