bug#81360: df -P seems to use wrong format

Hey.

As per POSIX when using -P, the format should be as given in the STDOUT
section of the page below:
https://pubs.opengroup.org/onlinepubs/9799919799/utilities/df.html

POSIX has no type column at all, the headers don't match either and the
values should be in 512B or 1KiB units.


Kinda defeats the purpose of the -P option if it then doens't use POSIX
output? :-)


Cheers,
Chris.