libblkid: detect CD/DVD discs in packet writing mode

libblkid: detect CD/DVD discs in packet writing mode

Packet writing mode for CD and DVD discs is provided by kernel module
pktcdvd.ko which exports block devices /dev/pktcdvd/pktcdvd*.

These block devices do not accept CDROM_DRIVE_STATUS ioctl, therefore
current blkid code does not detect them as BLKID_FL_CDROM_DEV and also
does not do necessary size correction.

Extend detection of CD/DVD discs by additional CDROM_LAST_WRITTEN ioctl
which is accepted also by pktcdvd.ko.

Signed-off-by: Pali Rohár <pali.rohar@gmail.com>