cfg80211: move offchan_cac_event to a dedicated work

cfg80211: move offchan_cac_event to a dedicated work

In order to make cfg80211_offchan_cac_abort() (renamed from
cfg80211_offchan_cac_event) callable in other contexts and
without so much locking restrictions, make it trigger a new
work instead of operating directly.

Do some other renames while at it to clarify.

Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Link: https://lore.kernel.org/r/6145c3d0f30400a568023f67981981d24c7c6133.1635325205.git.lorenzo@kernel.org
[rewrite commit log]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>