lsblk: add dependence between CD/DVD block and packet devices

lsblk: add dependence between CD/DVD block and packet devices

This dependence is defined by

  $ cat /sys/class/pktcdvd/device_map
  pktcdvd0 252:0 11:0

Unfortunately, there is not any direct sysfs way how to refer this
relationship in /sys/{block,dev/block}. So, we have to read the
device_map file and then compare device numbers with the list.

$ lsblk /dev/sr0
NAME       MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sr0         11:0    1 1024M  0 rom
└─pktcdvd0 252:0    1    0B  0 disk

Addresses: https://github.com/karelzak/util-linux/issues/1185
Signed-off-by: Karel Zak <kzak@redhat.com>