fix compile warning.

git-svn-id: https://rt-thread.googlecode.com/svn/trunk@2446 bbd45198-f89e-11dd-88c7-29a3b14d5316

components/drivers/usb/usbhost/core/driver.c

@@ -13,7 +13,8 @@
  */
 
 #include <rtthread.h>
-#include <drivers/usb_host.h>
+#include <rtservice.h>
+#include <rtdevice.h>
 
 static rt_list_t _driver_list;