libnm-util: fix some introspection annotations

libnm-util/nm-setting.c

@@ -999,7 +999,8 @@ nm_setting_to_string (NMSetting *setting)
  * Returns the name of the virtual kernel interface which the connection
  * needs to use if specified in the settings.
  *
- * Returns: (transfer full) (element-type utf8): Name of the virtual interface
+ * Returns: Name of the virtual interface or %NULL if the setting does not
+ * support this feature
  **/
 const char *
 nm_setting_get_virtual_iface_name (NMSetting *setting)

libnm-util/nm-utils.c

@@ -2488,8 +2488,8 @@ nm_utils_hwaddr_aton (const char *asc, int type, gpointer buffer)
  * Parses @asc and converts it to binary form in a #GByteArray. See
  * nm_utils_hwaddr_aton() if you don't want a #GByteArray.
  *
- * Return value: a new #GByteArray, or %NULL if @asc couldn't be
- * parsed
+ * Return value: (transfer full): a new #GByteArray, or %NULL if @asc couldn't
+ * be parsed
  */
 GByteArray *
 nm_utils_hwaddr_atoba (const char *asc, int type)