cfg80211: call cfg80211_stop_ap when switch from P2P_GO type

If the userspace tools switch from NL80211_IFTYPE_P2P_GO to
NL80211_IFTYPE_ADHOC via send_msg(NL80211_CMD_SET_INTERFACE), it
does not call the cleanup cfg80211_stop_ap(), this leads to the
initialization of in-use data. For example, this path re-init the
sdata->assigned_chanctx_list while it is still an element of
assigned_vifs list, and makes that linked list corrupt.

Signed-off-by: Nguyen Dinh Phi <phind.uet@gmail.com>
Reported-by:  <syzbot+bbf402b783eeb6d908db@syzkaller.appspotmail.com>
Link: https://lore.kernel.org/r/20211027173722.777287-1-phind.uet@gmail.com
Cc: stable@vger.kernel.org
Fixes: ac800140

 ("cfg80211: .stop_ap when interface is going down")
Signed-off-by: Johannes Berg <johannes.berg@intel.com>