mac80211_hwsim: add channel switch support

Advertise to mac80211 that we can do channel switch both
for STA and AP/GO.
After each beacon transmission check if CSA is done and
call ieee80211_csa_finish if needed.

Signed-off-by: Andrei Otcheretianski <andrei.otcheretianski@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>