Refactor sent extension message output

Signed-off-by: Jerry Yu <jerry.h.yu@arm.com>
diff --git a/library/ssl_tls13_generic.c b/library/ssl_tls13_generic.c
index a94bbef..1a17372 100644
--- a/library/ssl_tls13_generic.c
+++ b/library/ssl_tls13_generic.c
@@ -887,6 +887,8 @@
 
     *out_len = p - buf;
 
+    MBEDTLS_SSL_PRINT_SENT_EXTS( 3, MBEDTLS_SSL_HS_CERTIFICATE );
+
     return( 0 );
 }