All the TNC base64 operations are within tncs.c, so there is no point in
including base64.h into eap_server_tnc.c.
Signed-hostap: Jouni Malinen <j@w1.fi>
62477841a1 tried to address fragmentation
issues, but it did not address the case where the final EAP-TNC
message gets fragmented. Move the state update to the correct place
to address this case, too.