Reimplement disk_info() function

Reimplement disk_info() function

The disklist variable holds a newline separated list of devices that is
used to get various infos about the given disks, such as sfdisk,
smartctl, hdparm, fdisk, parted, sdparm, sg_inq and the output of file.

Unfortunately NVMe disks were not included in the list.

lsblk lists information about all available or specified block devices
excluding the loopback and CD-ROM devices. The checkdisk() function is
is no longer needed.

FTR, the major:minor device numbers are listed in the Kernel
documentation, in case we need to exclude more disk device types:

https://www.kernel.org/doc/Documentation/admin-guide/devices.txt

Closes: grml/grml-hwinfo#6