iwlwifi: mvm: Use beacon_get_template instead of beacon_get

Call ieee80211_beacon_get_template instead of ieee80211_beacon_get and sync the
CSA counters with mac80211 after each beacon transmission.

Signed-off-by: Andrei Otcheretianski <andrei.otcheretianski@intel.com>
Reviewed-by: Luciano Coelho <luciano.coelho@intel.com>
Reviewed-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>