drm/i915: disable all crtcs at suspend time

We need this to avoid confusing the hw state readout code with the cpt
pch plls at resume time: We'd read the new pipe state (which is
disabled), but still believe that we have a life pll connected to that
pipe (from before the suspend). Hence properly disable pipes to clear
out all the residual state.

This has the neat side-effect that we don't enable ports prematurely
by restoring bogus state from the saved register values.

Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-Off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_drv.c

@@ -470,6 +470,9 @@ static int i915_drm_freeze(struct drm_device *dev)
 				"GEM idle failed, resume might fail\n");
 			return error;
 		}
+
+		intel_modeset_disable(dev);
+
 		drm_irq_uninstall(dev);
 	}