Add entry for PSK extension

Reviewed-by: NRich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/2747)

ssl/t1_trce.c

@@ -455,6 +455,7 @@ static ssl_trace_tbl ssl_exts_tbl[] = {
     {TLSEXT_TYPE_server_authz, "server_authz"},
     {TLSEXT_TYPE_cert_type, "cert_type"},
     {TLSEXT_TYPE_key_share, "key_share"},
+    {TLSEXT_TYPE_psk, "psk"},
     {TLSEXT_TYPE_psk_kex_modes, "psk_key_exchange_modes"},
     {TLSEXT_TYPE_supported_groups, "supported_groups"},
     {TLSEXT_TYPE_ec_point_formats, "ec_point_formats"},