io_uring: fix wrong arm_poll error handling

Leaving ip.error set when a request was punted to task_work execution is
problematic, don't forget to clear it.

Fixes: aa43477 ("io_uring: poll rework")
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/a6c84ef4182c6962380aebe11b35bdcb25b0ccfb.1655852245.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

fs/io_uring.c

@@ -7145,6 +7145,7 @@ static int __io_arm_poll_handler(struct io_kiocb *req,
 		if (unlikely(ipt->error || !ipt->nr_entries)) {
 			poll->events |= EPOLLONESHOT;
 			req->apoll_events |= EPOLLONESHOT;
+			ipt->error = 0;
 		}
 		__io_poll_execute(req, mask, poll->events);
 		return 0;