lsblk: don't ignore dependences for partitioned devies

lsblk: don't ignore dependences for partitioned devies

The code only lists partitions, but ignore another dependencies
on whole-disk device:

	$ lsblk /dev/sdb
	NAME   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
	sdb      8:16   0 298.1G  0 disk
	└─sdb1   8:17   0 298.1G  0 part

	$ ls /sys/block/sdb/holders/
	dm-0

fixed version:

	$ lsblk /dev/sdb
	NAME        MAJ:MIN RM   SIZE RO TYPE  MOUNTPOINT
	sdb           8:16   0 298.1G  0 disk
	├─sdb1        8:17   0 298.1G  0 part
	└─mpatha    253:0    0 298.1G  0 mpath
	  └─mpatha1 253:1    0 298.1G  0 part

Signed-off-by: Karel Zak <kzak@redhat.com>