Limit the current implementation to a single channel context used by
a single vif, thereby avoiding multi-vif/channel complexities.
Reuse the main function from AP CSA code, but move a portion out in
order to fit the STA scenario.
Add a new mac80211 HW flag so we don't break devices that don't support
channel switch with channel-contexts. The new behavior will be opt-in.
Signed-off-by: Arik Nemtsov <arik@wizery.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
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