mac80211: add api to set CSA counter in mac80211

Sometimes the most updated CSA counter values are known only
to the device. Add an API to pass this data to mac80211.

Signed-off-by: Gregory Greenman <gregory.greenman@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>