Change cookie free code and some comments

Signed-off-by: XiaokangQian <xiaokang.qian@arm.com>
diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index 6f37201..82da11f 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -5689,11 +5689,11 @@
     mbedtls_pk_free( &handshake->peer_pubkey );
 #endif /* MBEDTLS_X509_CRT_PARSE_C && !MBEDTLS_SSL_KEEP_PEER_CERTIFICATE */
 
-#if defined(MBEDTLS_SSL_PROTO_DTLS)
+#if defined(MBEDTLS_SSL_PROTO_DTLS) || defined(MBEDTLS_SSL_PROTO_TLS1_3)
     mbedtls_free( handshake->verify_cookie );
     mbedtls_ssl_flight_free( handshake->flight );
     mbedtls_ssl_buffering_free( ssl );
-#endif
+#endif /* MBEDTLS_SSL_PROTO_DTLS || MBEDTLS_SSL_PROTO_TLS1_3 */
 
 #if defined(MBEDTLS_ECDH_C) &&                  \
     defined(MBEDTLS_USE_PSA_CRYPTO)