1. support for iar in situation of usb host application

core/usbh_core.c

@@ -690,8 +690,6 @@ int usbh_initialize(void)
     usbh_class_info_table_begin = (struct usbh_class_info *)&__usbh_class_info_start__;
     usbh_class_info_table_end = (struct usbh_class_info *)&__usbh_class_info_end__;
 #elif defined(__ICCARM__) || defined(__ICCRX__)
-    extern uint32_t __usbh_class_info_start__;
-    extern uint32_t __usbh_class_info_end__;
     usbh_class_info_table_begin = (struct usbh_class_info *)__section_begin("usbh_class_info");
     usbh_class_info_table_end = (struct usbh_class_info *)__section_end("usbh_class_info");
 #endif