AP: Add support for full station state

AP: Add support for full station state

Add support for drivers that support full AP client state, i.e., can
handle adding stations that are not associated yet. For such drivers,
add a station after processing the authentication request, instead of
adding it in the association response callback.

Doing so is beneficial in cases where the driver cannot handle the add
station request, in which case it is useless to perform the complete
connection establishment.

Signed-off-by: Ayala Beker <ayala.beker@intel.com>