improve comments

Signed-off-by: Jerry Yu <jerry.h.yu@arm.com>
diff --git a/library/ssl_ticket.c b/library/ssl_ticket.c
index 05249ea..5fef4eb 100644
--- a/library/ssl_ticket.c
+++ b/library/ssl_ticket.c
@@ -518,7 +518,7 @@
             goto cleanup;
         }
     }
-#endif
+#endif /* MBEDTLS_SSL_PROTO_TLS1_2 */
 #endif /* MBEDTLS_HAVE_TIME */
 
 cleanup: