mac80211: Reorder debugfs calls during netdev deinit

ieee80211_free_keys() must be called before
ieee80211_debugfs_remove_netdev() in order to make sure that the
possible default_key symlink is removed before attempting to
remove the netdev debugfs directory.

Signed-off-by: Jouni Malinen <jouni.malinen@atheros.com>
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>