drm/dp_mst: Correct the bug in drm_dp_update_payload_part1()

[Why]
If the payload_state is DP_PAYLOAD_DELETE_LOCAL in series, current
code doesn't delete the payload at current index and just move the
index to next one after shuffling payloads.

[How]
Drop the i++ increasing part in for loop head and decide whether
to increase the index or not according to payload_state of current
payload.

Changes since v1:
* Refine the code to have it easy reading
* Amend the commit message to meet the way code is modified now.
Signed-off-by: Wayne Lin <Wayne.Lin@amd.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>
Fixes: 706246c7 ("drm/dp_mst: Refactor drm_dp_update_payload_part1()")
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Juston Li <juston.li@intel.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Sean Paul <sean@poorly.run>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: dri-devel@lists.freedesktop.org
Cc: <stable@vger.kernel.org> # v5.1+
[Added cc for stable]
Signed-off-by: Lyude Paul <lyude@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191203042423.5961-1-Wayne.Lin@amd.com

drivers/gpu/drm/drm_dp_mst_topology.c

@@ -3176,9 +3176,11 @@ int drm_dp_update_payload_part1(struct drm_dp_mst_topology_mgr *mgr)
 			drm_dp_mst_topology_put_port(port);
 	}
 
-	for (i = 0; i < mgr->max_payloads; i++) {
-		if (mgr->payloads[i].payload_state != DP_PAYLOAD_DELETE_LOCAL)
+	for (i = 0; i < mgr->max_payloads; /* do nothing */) {
+		if (mgr->payloads[i].payload_state != DP_PAYLOAD_DELETE_LOCAL) {
+			i++;
 			continue;
+		}
 
 		DRM_DEBUG_KMS("removing payload %d\n", i);
 		for (j = i; j < mgr->max_payloads - 1; j++) {