Remove user space client MLME

Remove user space client MLME

This code was used only with driver_test.c to allow MLME operations
in hostapd to be tested without having to use a real radio. There
are no plans on extending this to any other use than testing and
mac80211_hwsim has now obsoled the need for this type of testing.
As such, we can drop this code from wpa_supplicant to clean up the
implementation of unnecessary complexity.