Fix output initialization

Summary: Fixes a regression where displays would not be available to kscreen.

Test Plan: Can configure my screens again.

Reviewers: davidedmundson

Reviewed By: davidedmundson

Subscribers: kwin

Tags: #kwin

Differential Revision: https://phabricator.kde.org/D28243

abstract_wayland_output.cpp

@@ -277,6 +277,7 @@ void AbstractWaylandOutput::initInterfaces(const QString &model, const QString &
 
     // start off enabled
     m_waylandOutput->create();
+    m_waylandOutputDevice->create();
     m_xdgOutput->setLogicalSize(pixelSize() / scale());
     m_xdgOutput->done();
 }