util-linux: bump to version 2.31.1

Changes in this version:

- Small improvement and bug fixes.
- Install rfkill at /usr/sbin (thus overriding the one eventually
  installed by BusyBox).

Drop the md5 patch, already applyed upstream.

Signed-off-by: Carlos Santos <casantos@datacom.ind.br>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>