Set orientation from DRM on fallback
Summary:
In case of a failed atomic commit the previous mode should be fallen back to.
For orientation provide again a setter that DRM backend can use to set the
transform back to the last working one.
Test Plan: Compiles, fallback works, cursor still messed up somewhat (scaling issue?).
Reviewers: KWin
Subscribers: zzag, kwin
Tags: KWin
Maniphest Tasks: T11670
Differential Revision: https://phabricator.kde.org/D25507