[platforms/drm] Determine the supported transformation on a plane
Summary:
The idea behind getting the supported transformations is to tell KScreen
which transformations are actually supported and thus not even allow the
user select a setting which is not supported.
Reviewers: KWin, Plasma, subdiff
Subscribers: plasma-devel, kwin
Tags: KWin
Differential Revision: https://phabricator.kde.org/D8645