io_uring: dual license io_uring.h uapi header

to #28170604

commit bbbdeb4720a0759ec90e3bcb20ad28d19e531346 upstream

This just syncs the header it with the liburing version, so there's no
confusion on the license of the header parts.
Signed-off-by: NJens Axboe <axboe@kernel.dk>
Acked-by: NJoseph Qi <joseph.qi@linux.alibaba.com>
Signed-off-by: NXiaoguang Wang <xiaoguang.wang@linux.alibaba.com>

include/uapi/linux/io_uring.h

-/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note OR MIT */
 /*
  * Header file for the io_uring interface.
  *