mwifiex: don't short-circuit netdev notifiers on interface deletion

When we leave the delete interface function, there are still netdev
hooks that might try to process the device. We're short-circuiting some
of that by changing the interface type and clearing ieee80211_ptr. This
means we skip NETDEV_UNREGISTER_FINAL in cfg80211. Fortunately, that is
currently a no-op.

We don't need most of the cleanup here anyway:

 * the connection state will get (un)set as part of the disconnect
   process (which cfg80211 already initiates for us)
 * the interface type doesn't actually need to be cleared at all (it'll
   trigger a WARN_ON() in cfg80211 if we do)
 * the iee80211_ptr isn't really "ours" to clear anyway

So stop resetting those 3 things.

Signed-off-by: Brian Norris <briannorris@chromium.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>