Fix issue #86: tlp-stat: don't suggest tp-smapi on non-ThinkPad hardware
  with thinkpad_acpi loaded (sayantandas);
  is_thinkpad(), read_dmi() enhanced.
tlp-functions, get_disk_dev(): minor fix

Small fix for the unlikely case that the disk id $1
ends with a partition number >= 10 (contains one or more '0' chars).

Another (slightly less reliable) solution would be
the shell's builtin variable substitution:

  > disk_dev=${disk_id%%-part[0-9]*}
  ...
  > disk_dev=${disk_dev%%[0-9]*}

Signed-off-by: Thomas Koch <linrunner@gmx.net>