D7890: add size hint to KScreen KCM

[Aleix Pol Gonzalez]

apol added a comment.


  Thanks! this bothered me in the past :)

REPOSITORY
  R104 KScreen

REVISION DETAIL
  https://phabricator.kde.org/D7890

To: valeriymalov, #plasma, davidedmundson
Cc: apol, plasma-devel, ZrenBot, progwolff, lesliezhai, ali-mohamed, 
jensreuterberg, abetts, sebas, mart