iwlwifi: mvm: reduce active dwell time

Reduce basic active dwell time from 30 ms on 2.4 GHz and 20 on 5.2 to
20 on 2.4 and 10 on 5.2.

Signed-off-by: David Spinadel <david.spinadel@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>