io_uring: Remove redundant hrtimer's callback function setup

The IORING_OP_TIMEOUT command uses hrtimer underneath. The timer's callback
function is setup in io_timeout(), and then the callback function is setup
again when the timer is rearmed.

Since the callback function is the same for both cases, the latter setup is
redundant, therefore remove it.

Signed-off-by: Nam Cao <namcao@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Jens Axboe <axboe@kernel.dk:
Link: https://lore.kernel.org/all/07b28dfd5691478a2d250f379c8b90dd37f9bb9a.1730386209.git.namcao@linutronix.de

Author: covanam

io_uring/timeout.c

@@ -76,7 +76,6 @@ static void io_timeout_complete(struct io_kiocb *req, struct io_tw_state *ts)
 			/* re-arm timer */
 			spin_lock_irq(&ctx->timeout_lock);
 			list_add(&timeout->list, ctx->timeout_list.prev);
-			data->timer.function = io_timeout_fn;
 			hrtimer_start(&data->timer, timespec64_to_ktime(data->ts), data->mode);
 			spin_unlock_irq(&ctx->timeout_lock);
 			return;