mac80211: add supported channels IE during TDLS setup

This information element is mandatory in case TDLS channel-switching is to
be supported. The channels given are ones supported and allowed to be
active in the current regulatory setting.

Signed-off-by: Arik Nemtsov <arikx.nemtsov@intel.com>
Signed-off-by: Arik Nemtsov <arik@wizery.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>