Input: xen-kbdfront - make xenbus device ids constant

The ids field of the struct xenbus_device_id is constant in <linux/xen/xenbus.h>
so it makes sense to mark xenkbd_ids also constant.
Signed-off-by: Márton Németh <nm127@freemail.hu>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>

drivers/input/xen-kbdfront.c

@@ -321,7 +321,7 @@ static void xenkbd_backend_changed(struct xenbus_device *dev,
 	}
 }
 
-static struct xenbus_device_id xenkbd_ids[] = {
+static const struct xenbus_device_id xenkbd_ids[] = {
 	{ "vkbd" },
 	{ "" }
 };