backends/drm: Fix leaving dangling dpms input event filter

If the output is turned back on before m_turnOffTimer expires, the
dpms input event filter won't be reset and all input events will go to
the void.

BUG: 460322

src/backends/drm/drm_output.cpp

@@ -250,6 +250,7 @@ void DrmOutput::setDpmsMode(DpmsMode mode)
             m_gpu->platform()->createDpmsFilter();
         }
     } else {
+        m_gpu->platform()->checkOutputsAreOn();
         m_turnOffTimer.stop();
         if (mode != dpmsMode() && setDrmDpmsMode(mode)) {
             Q_EMIT wakeUp();