drm/dp_mst: Remove lies in {up, down}_rep_recv documentation

These are most certainly accessed from far more than the mgr work. In
fact, up_req_recv is -only- ever accessed from outside the mgr work.

Cc: Juston Li <juston.li@intel.com>
Cc: Imre Deak <imre.deak@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Harry Wentland <hwentlan@amd.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Lyude Paul <lyude@redhat.com>
Reviewed-by: Sean Paul <sean@poorly.run>
Link: https://patchwork.freedesktop.org/patch/msgid/20190903204645.25487-19-lyude@redhat.com

include/drm/drm_dp_mst_helper.h

@@ -481,15 +481,11 @@ struct drm_dp_mst_topology_mgr {
 	int conn_base_id;
 
 	/**
-	 * @down_rep_recv: Message receiver state for down replies. This and
-	 * @up_req_recv are only ever access from the work item, which is
-	 * serialised.
+	 * @down_rep_recv: Message receiver state for down replies.
 	 */
 	struct drm_dp_sideband_msg_rx down_rep_recv;
 	/**
-	 * @up_req_recv: Message receiver state for up requests. This and
-	 * @down_rep_recv are only ever access from the work item, which is
-	 * serialised.
+	 * @up_req_recv: Message receiver state for up requests.
 	 */
 	struct drm_dp_sideband_msg_rx up_req_recv;