iwlwifi: mvm: add adaptive dwell support

Update the scan command API with support for adaptive dwell.  Adaptive
dwell is a type of scan that dynamically changes the time it remains
on each channel listening for beacons or probe responses.

Signed-off-by: Roee Zamir <roee.zamir@intel.com>
Signed-off-by: Beni Lev <beni.lev@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>