io_uring: make spdxcheck.py happy

Commit bbbdeb47 ("io_uring: dual license io_uring.h uapi header")
uses a nested SPDX-License-Identifier to dual license the header.

Since then, ./scripts/spdxcheck.py complains:

  include/uapi/linux/io_uring.h: 1:60 Missing parentheses: OR

Add parentheses to make spdxcheck.py happy.
Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

include/uapi/linux/io_uring.h

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