drm/dp_mst: Fix all mstb marked as not probed after suspend/resume

[Why]
After supend/resume, with topology unchanged, observe that
link_address_sent of all mstb are marked as false even the topology probing
is done without any error.

It is caused by wrongly also include "ret == 0" case as a probing failure
case.

[How]
Remove inappropriate checking conditions.

Cc: Lyude Paul <[email protected]>
Cc: Harry Wentland <[email protected]>
Cc: Jani Nikula <[email protected]>
Cc: Imre Deak <[email protected]>
Cc: Daniel Vetter <[email protected]>
Cc: [email protected]
Fixes: 37dfdc5 ("drm/dp_mst: Cleanup drm_dp_send_link_address() a bit")
Signed-off-by: Wayne Lin <[email protected]>
Reviewed-by: Lyude Paul <[email protected]>
Signed-off-by: Lyude Paul <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]

Author: Wayne Lin

drivers/gpu/drm/display/drm_dp_mst_topology.c

@@ -2929,7 +2929,7 @@ static int drm_dp_send_link_address(struct drm_dp_mst_topology_mgr *mgr,
 
 	/* FIXME: Actually do some real error handling here */
 	ret = drm_dp_mst_wait_tx_reply(mstb, txmsg);
-	if (ret <= 0) {
+	if (ret < 0) {
 		drm_err(mgr->dev, "Sending link address failed with %d\n", ret);
 		goto out;
 	}
@@ -2981,7 +2981,7 @@ static int drm_dp_send_link_address(struct drm_dp_mst_topology_mgr *mgr,
 	mutex_unlock(&mgr->lock);
 
 out:
-	if (ret <= 0)
+	if (ret < 0)
 		mstb->link_address_sent = false;
 	kfree(txmsg);
 	return ret < 0 ? ret : changed;