D8752: [platforms/drm] At safety checks for the properties

[Martin Flöser]

graesslin added a dependent revision: D8776: [autotests] Add tests for DRM 
platform plugin.

REPOSITORY
  R108 KWin

BRANCH
  drm-property-safety

REVISION DETAIL
  https://phabricator.kde.org/D8752

To: graesslin, #kwin, #plasma, fvogt, subdiff
Cc: plasma-devel, kwin, ZrenBot, progwolff, lesliezhai, ali-mohamed, 
jensreuterberg, abetts, sebas, apol, mart