refactor usb device intf and ep register

class/printer/usbd_printer.c

@@ -46,12 +46,18 @@ static void printer_notify_handler(uint8_t event, void *arg)
     }
 }
 
-void usbd_printer_add_interface(usbd_class_t *devclass, usbd_interface_t *intf)
+struct usbd_interface *usbd_printer_alloc_intf(void)
 {
+    struct usbd_interface *intf = usb_malloc(sizeof(struct usbd_interface));
+    if (intf == NULL) {
+        USB_LOG_ERR("no mem to alloc intf\r\n");
+        return NULL;
+    }
+
     intf->class_handler = printer_class_request_handler;
     intf->custom_handler = NULL;
     intf->vendor_handler = NULL;
     intf->notify_handler = printer_notify_handler;
 
-    usbd_class_add_interface(devclass, intf);
-}
+    return intf;
+}

class/printer/usbd_printer.h

@@ -12,7 +12,8 @@
 extern "C" {
 #endif
 
-void usbd_printer_add_interface(usbd_class_t *devclass, usbd_interface_t *intf);
+/* Alloc printer interface driver */
+struct usbd_interface *usbd_printer_alloc_intf(void);
 
 #ifdef __cplusplus
 }