wifi: iwlwifi: mld: honor BSS_CHANGED_BEACON_ENABLED

wifi: iwlwifi: mld: honor BSS_CHANGED_BEACON_ENABLED

We should stick to mac80211's flow to start / stop beaconing. This
allows to stop beaconing before we remove the BIGTK.

Note that the start and stop beaconing flows are not exactly symmetric.
When we start beaconing, we just update the beacon template. We assume
that mac80211 won't update the beacons, if we're not supposed to be
sending it.

Also note that we now send the beacon template after the broadcast
station was added to the firmware: the broadcast station is added in
the start_ap() flow, while the beacon template is now added in the
link_changed() flow which happens later. This is not what we did
before this patch, but this sequence is supported by the firmware as
well.

Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Link: https://patch.msgid.link/20260511203428.cf10e5754171.I8022517c6c5aedb4b56fba30a5545de8f62dddbe@changeid
Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>