drm/atomic: Small documentation fix.

Use the correct function name for drm_atomic_clean_old_fb docs.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
index 91825e6..55b4deb 100644
--- a/drivers/gpu/drm/drm_atomic.c
+++ b/drivers/gpu/drm/drm_atomic.c
@@ -1430,7 +1430,7 @@
 }
 
 /**
- * drm_atomic_update_old_fb -- Unset old_fb pointers and set plane->fb pointers.
+ * drm_atomic_clean_old_fb -- Unset old_fb pointers and set plane->fb pointers.
  *
  * @dev: drm device to check.
  * @plane_mask: plane mask for planes that were updated.