io_uring: set @poll->file after @poll init

It's a good practice to modify fields of a struct after but not before
it was initialised. Even though io_init_poll_iocb() doesn't touch
poll->file, call it first.
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

fs/io_uring.c

@@ -4596,8 +4596,8 @@ static __poll_t __io_arm_poll_handler(struct io_kiocb *req,
 	struct io_ring_ctx *ctx = req->ctx;
 	bool cancel = false;
 
-	poll->file = req->file;
 	io_init_poll_iocb(poll, mask, wake_func);
+	poll->file = req->file;
 	poll->wait.private = req;
 
 	ipt->pt._key = mask;