drm/usb: fix module license on drm/usb layer.

Allows this module to load correctly with certain debugging options on.

Reported on irc by scientes
Signed-off-by: NDave Airlie <airlied@redhat.com>

drivers/gpu/drm/drm_usb.c

 #include "drmP.h"
 #include <linux/usb.h>
-#include <linux/export.h>
+#include <linux/module.h>
 
 int drm_get_usb_dev(struct usb_interface *interface,
 		    const struct usb_device_id *id,
@@ -114,3 +114,7 @@ void drm_usb_exit(struct drm_driver *driver,
 	usb_deregister(udriver);
 }
 EXPORT_SYMBOL(drm_usb_exit);
+
+MODULE_AUTHOR("David Airlie");
+MODULE_DESCRIPTION("USB DRM support");
+MODULE_LICENSE("GPL and additional rights");