io_uring: don't pass ctx to tw add remote helper

Unlike earlier versions, io_msg_remote_post() creates a valid request
with a proper context, so don't pass a context to
io_req_task_work_add_remote() explicitly but derive it from the request.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/721f51cf34996d98b48f0bfd24ad40aa2730167e.1743190078.git.asml.silence@gmail.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>