wifi: cfg80211: remove BSS pointer from cfg80211_disassoc_request

The race described by the comment in mac80211 hasn't existed
since the locking rework to use the same lock and for MLO we
need to pass the AP MLD address, so just pass the BSSID or
AP MLD address instead of the BSS struct pointer, and adjust
all the code accordingly.

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