cfg80211: fix phy80211 symlink creation

cfg80211: fix phy80211 symlink creation

When I moved around the code here, I neglected that we could still
call register_netdev() or similar without the wiphy mutex held,
which then calls cfg80211_register_wdev() - that's also done from
cfg80211_register_netdevice(), but the phy80211 symlink creation
was only there. Now, the symlink isn't needed for a *pure* wdev,
but a netdev not registered via cfg80211_register_wdev() should
still have the symlink, so move the creation to the right place.

Cc: stable@vger.kernel.org
Fixes: 2fe8ef106238 ("cfg80211: change netdev registration/unregistration semantics")
Link: https://lore.kernel.org/r/20210608113226.a5dc4c1e488c.Ia42fe663cefe47b0883af78c98f284c5555bbe5d@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>