drm/i915: Avoid circular locking from intel_fbdev_fini()

lockdep spots that the fb_info->lock takes the dev->struct_mutex during
init (due to the device probing) and so we can not hold
dev->struct_mutex when unregistering the framebuffer. Simply reverse the
order of initialisation during cleanup and so do the intel_fbdev_fini()
before the intel_modeset_cleanup.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
diff --git a/drivers/gpu/drm/i915/intel_fb.c b/drivers/gpu/drm/i915/intel_fb.c
index 7af4acc..7dc50ac 100644
--- a/drivers/gpu/drm/i915/intel_fb.c
+++ b/drivers/gpu/drm/i915/intel_fb.c
@@ -206,8 +206,8 @@
 	.fb_probe = intel_fb_find_or_create_single,
 };
 
-static int intel_fbdev_destroy(struct drm_device *dev,
-			       struct intel_fbdev *ifbdev)
+static void intel_fbdev_destroy(struct drm_device *dev,
+				struct intel_fbdev *ifbdev)
 {
 	struct fb_info *info;
 	struct intel_framebuffer *ifb = &ifbdev->ifb;
@@ -225,9 +225,7 @@
 
 	drm_framebuffer_cleanup(&ifb->base);
 	if (ifb->obj)
-		drm_gem_object_unreference(ifb->obj);
-
-	return 0;
+		drm_gem_object_unreference_unlocked(ifb->obj);
 }
 
 int intel_fbdev_init(struct drm_device *dev)