EAP-AKA: Add Session-Id derivation during fast-reauth

EAP-AKA: Add Session-Id derivation during fast-reauth

The Session-Id derivation for EAP-AKA in RFC 5247 only explained how the
Session-Id is derived for regular authentication. Jouni reported it as
an errata with text explaining how to derive it during fast
reauthentication.

This patch now exports the Session-Id for EAP-AKA during fast
reauthentication based on this Session-Id = 0x17 || NONCE_S || MAC
construction.

Also documented by Alan Dekok in draft-dekok-emu-eap-session-id.

Signed-off-by: Mohit Sethi <mohit.sethi@aalto.fi>