drm: remove excess description

Description of expected_size doesn't match any parameter of the function
drm_atomic_replace_property_blob. Removing it.

Signed-off-by: Luis de Bethencourt <luisbg@osg.samsung.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1458408156-15990-1-git-send-email-luisbg@osg.samsung.com

drivers/gpu/drm/drm_atomic.c

@@ -392,7 +392,6 @@ EXPORT_SYMBOL(drm_atomic_set_mode_prop_for_crtc);
  * drm_atomic_replace_property_blob - replace a blob property
  * @blob: a pointer to the member blob to be replaced
  * @new_blob: the new blob to replace with
- * @expected_size: the expected size of the new blob
  * @replaced: whether the blob has been replaced
  *
  * RETURNS: