Revert "D-Bus: Implement Pmf property"

Revert "D-Bus: Implement Pmf property"

This reverts commit adf8f45f8af27a9ac9429ecde81776b19b6f9224.

It is basically all wrong. The Pmf property did exist, with a signature of
"s" as documented in doc/dbus.doxygen. It was synthesized from
global_fields[].

The patch added a duplicate one, with a signature of "u", in violation
of D-Bus specification and to bemusement of tools that are careful
enough:

  $ busctl introspect fi.w1.wpa_supplicant1 /fi/w1/wpa_supplicant1/Interfaces/666
  Duplicate property

Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>