Fix missing fields in ssl session struct comment

The endpoint and version were factorized out into the main session.
Update the session struct comment to reflect these new fields, as was
previously missed.

Signed-off-by: David Horstmann <david.horstmann@arm.com>

library/ssl_tls.c

@@ -4180,6 +4180,8 @@ static const unsigned char ssl_serialized_session_header[] = {
  *    uint8_t minor_ver;           // Protocol minor version. Possible values:
  *                                 // - TLS 1.2 (0x0303)
  *                                 // - TLS 1.3 (0x0304)
+ *    uint8_t endpoint;
+ *    uint16_t ciphersuite;
  *
  *    select (serialized_session.tls_version) {
  *