wifi: mac80211: move offchannel works to wiphy work

[ Upstream commit 97c19e42 ]

Make the offchannel works wiphy works to have the
wiphy locked for executing them.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Stable-dep-of: eadfb547 ("wifi: mac80211: move sched-scan stop work to wiphy work")
Signed-off-by: Sasha Levin <sashal@kernel.org>