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 int cdrom_dvdram_open_write(struct cdrom_device_info *cdi)
{
	int ret = cdrom_media_erasable(cdi);

	/*
	 * allow writable open if media info read worked and media is
	 * erasable, _or_ if it fails since not all drives support it
	 */
	if (!ret)
		return 1;

	return 0;
}

static int cdrom_dvdram_open_write(struct cdrom_device_info *cdi)
{
	int ret = cdrom_media_erasable(cdi);

	/*
	 * allow writable open if media info read worked and media is
	 * erasable, _or_ if it fails since not all drives support it
	 */
	if (!ret)
		return 1;

	return 0;
}
