drm/i915: fixup overlay stolen memory leak

We need to clean up the overlay first, before taking down the
stolen memory allocator.

This regression has been introducec in

commit 80405138
Author: Chris Wilson <chris@chris-wilson.co.uk>
Date:   Thu Nov 15 11:32:29 2012 +0000

    drm/i915: Allocate overlay registers from stolen memory

v2: Rework the patch a bit as suggested by Chris Wilson:
- move the overlay teardown up, into the modeset cleanup
- move the stolen mm takedown into i915_gem_cleanup_stolen

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_dma.c

@@ -1737,9 +1737,6 @@ int i915_driver_unload(struct drm_device *dev)
 		mutex_unlock(&dev->struct_mutex);
 		i915_gem_cleanup_aliasing_ppgtt(dev);
 		i915_gem_cleanup_stolen(dev);
-		drm_mm_takedown(&dev_priv->mm.stolen);
-
-		intel_cleanup_overlay(dev);
 
 		if (!I915_NEED_GFX_HWS(dev))
 			i915_free_hws(dev);

drivers/gpu/drm/i915/i915_gem_stolen.c

@@ -173,7 +173,10 @@ void i915_gem_stolen_cleanup_compression(struct drm_device *dev)
 
 void i915_gem_cleanup_stolen(struct drm_device *dev)
 {
+	struct drm_i915_private *dev_priv = dev->dev_private;
+
 	i915_gem_stolen_cleanup_compression(dev);
+	drm_mm_takedown(&dev_priv->mm.stolen);
 }
 
 int i915_gem_init_stolen(struct drm_device *dev)

drivers/gpu/drm/i915/intel_display.c

@@ -8869,6 +8869,8 @@ void intel_modeset_cleanup(struct drm_device *dev)
 	flush_scheduled_work();
 
 	drm_mode_config_cleanup(dev);
+
+	intel_cleanup_overlay(dev);
 }
 
 /*