wifi: mac80211: always hold sdata lock in chanctx assign/unassign

Due to all the multi-link handling, we now expose the fact that
the sdata/vif is locked to drivers, e.g. when the driver uses
ieee80211_set_monitor_channel(). This was true when a chanctx
is added to or removed from a link, _except_ in monitor mode
with the virtual sdata/vif. Change that, so that drivers can
make that assumption.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Gregory Greenman <gregory.greenman@intel.com>
Link: https://lore.kernel.org/r/20230619161906.a5cf7534beda.I5b51664231abee27e02f222083df7ccf88722929@changeid


Signed-off-by: Johannes Berg <johannes.berg@intel.com>