io_uring: Fix __io_uring_register() false success

If io_copy_iov() fails, it will break the loop and report success,
albeit partially completed operation.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

fs/io_uring.c

@@ -2616,7 +2616,7 @@ static int io_sqe_buffer_register(struct io_ring_ctx *ctx, void __user *arg,
 
 		ret = io_copy_iov(ctx, &iov, arg, i);
 		if (ret)
-			break;
+			goto err;
 
 		/*
 		 * Don't impose further limits on the size and buffer