eap-peap: Initiate Phase 2 immediately for TLS 1.3

Before TLS 1.3, the server sent the last handshake message and had the
option to piggyback the EAP-Identity request directly onto the packet
with the TLS Finished message, or wait for the empty message by the
client that acknowledges the completion of the handshake.  With TLS 1.3,
the client finishes the handshake after the server.  So this option
is irrelevant there and we immediately start with Phase 2.

src/libcharon/plugins/eap_peap/eap_peap_server.h

@@ -24,6 +24,7 @@
 
 typedef struct eap_peap_server_t eap_peap_server_t;
 
+#include "tls.h"
 #include "tls_application.h"
 
 #include <library.h>
@@ -38,6 +39,14 @@ struct eap_peap_server_t {
 	 * Implements the TLS application data handler.
 	 */
 	tls_application_t application;
+
+	/**
+	 * Set a reference to the parent TLS connection this application is
+	 * assigned to.
+	 *
+	 * @param tls		TLS connection
+	 */
+	void (*set_tls)(eap_peap_server_t *this, tls_t *tls);
 };
 
 /**