cfg80211: always free wiphy specific regdomain

In the (somewhat unlikely) event that we allocate a wiphy, then
add a regdomain to it, and then fail registration, we leak the
regdomain. Fix this by just always freeing it at the end, in the
normal cases we'll free (and NULL) it during wiphy_unregister().
This happened when the wiphy settings were bad, and since they
can be controlled by userspace with hwsim, syzbot was able to
find this issue.

Reported-by:  <syzbot+1638e7c770eef6b6c0d0@syzkaller.appspotmail.com>
Fixes: 3e0c3ff3 ("cfg80211: allow multiple driver regulatory_hints()")
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Link: https://lore.kernel.org/r/20210927131105.68b70cef4674.I4b9f0aa08c2af28555963b9fe3d34395bb72e0cc@changeid


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