r92su: replace sta_table with (rcu) sta_list

Signed-off-by: Christian Lamparter <chunkeey@googlemail.com>
r92su: disconnect before unregister module

Signed-off-by: Christian Lamparter <chunkeey@googlemail.com>
r92su: notify the user about usb errors

Signed-off-by: Christian Lamparter <chunkeey@googlemail.com>
r92su: move noht module parameter into common code

Signed-off-by: Christian Lamparter <chunkeey@googlemail.com>
r92su: make unexpected cmd seq message less obnoxious

Signed-off-by: Christian Lamparter <chunkeey@googlemail.com>