io_uring: Remove unnecessary null check

Null check kfree is redundant, so remove it.
This is detected by coccinelle.
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

fs/io_uring.c

@@ -1160,7 +1160,6 @@ static void __io_req_aux_free(struct io_kiocb *req)
 {
 	struct io_ring_ctx *ctx = req->ctx;
 
-	if (req->io)
 	kfree(req->io);
 	if (req->file) {
 		if (req->flags & REQ_F_FIXED_FILE)