cdrom: fix improper type cast, which can leat to information leak.

There is another cast from unsigned long to int which causes
a bounds check to fail with specially crafted input. The value is
then used as an index in the slot array in cdrom_slot_status().

This issue is similar to CVE-2018-16658 and CVE-2018-10940.

Signed-off-by: Young_X <YangX92@hotmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
static noinline int mmc_ioctl_cdrom_last_written(struct cdrom_device_info *cdi,
						 void __user *arg)
{
	int ret;
	long last = 0;
	cd_dbg(CD_DO_IOCTL, "entering CDROM_LAST_WRITTEN\n");
	ret = cdrom_get_last_written(cdi, &last);
	if (ret)
		return ret;
	if (copy_to_user((long __user *)arg, &last, sizeof(last)))
		return -EFAULT;
	return 0;
}

static noinline int mmc_ioctl_cdrom_last_written(struct cdrom_device_info *cdi,
						 void __user *arg)
{
	int ret;
	long last = 0;
	cd_dbg(CD_DO_IOCTL, "entering CDROM_LAST_WRITTEN\n");
	ret = cdrom_get_last_written(cdi, &last);
	if (ret)
		return ret;
	if (copy_to_user((long __user *)arg, &last, sizeof(last)))
		return -EFAULT;
	return 0;
}
