[Kernel] fix the compiling warning.

src/device.c

@@ -160,7 +160,7 @@ rt_device_t rt_device_create(int type, int attach_size)
     if (device)
     {
         rt_memset(device, 0x0, sizeof(struct rt_device));
-		device->type = type;
+        device->type = (enum rt_device_class_type)type;
     }
 
     return device;

src/object.c

@@ -522,7 +522,7 @@ rt_object_t rt_object_find(const char *name, rt_uint8_t type)
     /* try to find object */
     if (information == RT_NULL)
     {
-        information = rt_object_get_information(type);
+        information = rt_object_get_information((enum rt_object_class_type)type);
         RT_ASSERT(information != RT_NULL);
     }
     for (node  = information->object_list.next;