platforms/drm: fix dpms tracking

Since !844 (merged) DrmGpu::updateOutputs is changing the state of some drm properties without changing the fitting output state (RenderLoop inhibition) which can lead to rendering being inhibited indefinitely in some situations. In my specific case it happens when my laptop goes into dpms off and then suspends - it does turn on again but nothing is ever rendered, all you can do is move the mouse cursor and switch to a tty.