wifi: mac80211: Add non-atomic station iterator

wifi: mac80211: Add non-atomic station iterator

Drivers may at times want to iterate their stations with a function
which requires some non-atomic operations.

ieee80211_iterate_stations_mtx() introduces an API to iterate stations
while holding that wiphy's mutex. This allows the iterating function to
do non-atomic operations safely.

Signed-off-by: Rory Little <rory@candelatech.com>
Link: https://patch.msgid.link/20240806004024.2014080-2-rory@candelatech.com
[unify internal list iteration functions]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>