iwlwifi: mvm: support FTM responder

Add support for FTM responder for hardware/firmware combinations
that advertise support for it.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Avraham Stern <avraham.stern@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>