Get rid of wpa_supplicant_sta_rx() and add a new driver event that is
marked to be used only with driver_test.c. In addition, remove this
functionality from privsep wrapper. This is only use for client mode
MLME testing with driver_test.c.
This gets rid of previously deprecated driver_ops handlers set_wpa,
set_drop_unencrypted, set_auth_alg, set_mode. The same functionality
can be achieved by using the init/deinit/associate handlers.