io_uring: remove WRITE_ONCE() in io_uring_create()

io_uring: remove WRITE_ONCE() in io_uring_create()

There's no need to use WRITE_ONCE() to set ctx->submitter_task in
io_uring_create() since no other task can access the io_ring_ctx until a
file descriptor is associated with it. So use a normal assignment
instead of WRITE_ONCE().

Signed-off-by: Caleb Sander Mateos <csander@purestorage.com>
Link: https://lore.kernel.org/r/20250904161223.2600435-1-csander@purestorage.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>