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_flush_cache(struct cdrom_device_info *cdi)
{
	struct packet_command cgc;

	init_cdrom_command(&cgc, NULL, 0, CGC_DATA_NONE);
	cgc.cmd[0] = GPCMD_FLUSH_CACHE;

	cgc.timeout = 5 * 60 * HZ;

	return cdi->ops->generic_packet(cdi, &cgc);
}

static int cdrom_flush_cache(struct cdrom_device_info *cdi)
{
	struct packet_command cgc;

	init_cdrom_command(&cgc, NULL, 0, CGC_DATA_NONE);
	cgc.cmd[0] = GPCMD_FLUSH_CACHE;

	cgc.timeout = 5 * 60 * HZ;

	return cdi->ops->generic_packet(cdi, &cgc);
}
