fix comments and time_t type issues

Signed-off-by: Jerry Yu <jerry.h.yu@arm.com>
diff --git a/include/mbedtls/mbedtls_config.h b/include/mbedtls/mbedtls_config.h
index ed673e7..6d50c8d 100644
--- a/include/mbedtls/mbedtls_config.h
+++ b/include/mbedtls/mbedtls_config.h
@@ -1546,7 +1546,7 @@
  *
  * Size in bytes of a ticket nonce. This is not used in TLS 1.2.
  *
- * This must be smaller or equal to 255.
+ * This must be less than 256.
  */
 #define MBEDTLS_SSL_TICKET_NONCE_LENGTH 32