Switch from using driver specific ar->conf_mutex to wiphy->mtx. The benefits are:
* one lock less and simplified locking
* possibility to use wiphy_work_queue() without other locks
Most of the mac80211 ops are called within wiphy_lock(), most notable exception
being tx op. This can be checked with lockdep_assert_wiphy() from
net/mac80211/driver-ops.[ch] and I veried that by manually going through all
the ops in ath12k_ops which had lockdep_assert_wiphy().
The conversion was simple:
* All conf_mutex lock() and unlock() calls which
already were called under wiphy_lock() I replaced with
lockdep_assert_wiphy().
* The rest of conf_mutex calls I replaced with wiphy_lock() and wiphy_unlock().
* All lockdep_asset_held(conf_mutex) calls I replaced with
lockdep_assert_wiphy().
One exception was in ath12k_core_post_reconfigure_recovery() where the wiphy
lock needs to be taken before hw_mutex to avoid a lockdep warning.