net/kcm: convert kcm_ioctl() to FD_PREPARE()

	}

	case SIOCKCMCLONE: {

		struct kcm_clone info;

		struct file *file;

		info.fd = get_unused_fd_flags(0);

		if (unlikely(info.fd < 0))

			return info.fd;

		FD_PREPARE(fdf, 0, kcm_clone(sock));

		if (fdf.err)

			return fdf.err;

		file = kcm_clone(sock);

		if (IS_ERR(file)) {

			put_unused_fd(info.fd);

			return PTR_ERR(file);

		}

		if (copy_to_user((void __user *)arg, &info,

				 sizeof(info))) {

			put_unused_fd(info.fd);

			fput(file);

		info.fd = fd_prepare_fd(fdf);

		if (copy_to_user((void __user *)arg, &info, sizeof(info)))

			return -EFAULT;

		}

		fd_install(info.fd, file);

		fd_publish(fdf);

		err = 0;

		break;

	}