drm/i915: disable stolen mem for OVERLAY_NEEDS_PHYSICAL

Our phys_object code can't deal with stolen memory and so blows up.
Fixing this is quite a bit of work and not worth it much for a single
page object, so just opt-out.

This is necessary prep work to enable stolen on gen2/3 platforms where
the overlay register file isn't stored in the gtt.

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

drivers/gpu/drm/i915/intel_overlay.c

@@ -1333,6 +1333,8 @@ void intel_setup_overlay(struct drm_device *dev)
 
 	overlay->dev = dev;
 
+	reg_bo = NULL;
+	if (!OVERLAY_NEEDS_PHYSICAL(dev))
 		reg_bo = i915_gem_object_create_stolen(dev, PAGE_SIZE);
 	if (reg_bo == NULL)
 		reg_bo = i915_gem_alloc_object(dev, PAGE_SIZE);