drm/dp/mst: fix a possible memory leak in fetch_monitor_name()

drm_dp_mst_get_edid call kmemdup to create mst_edid. So mst_edid need to be
freed after use.
Signed-off-by: Hangyu Hua <hbh25y@gmail.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>
Signed-off-by: Lyude Paul <lyude@redhat.com>
Cc: stable@vger.kernel.org
Link: https://patchwork.freedesktop.org/patch/msgid/20220516032042.13166-1-hbh25y@gmail.com

drivers/gpu/drm/dp/drm_dp_mst_topology.c

@@ -4852,6 +4852,7 @@ static void fetch_monitor_name(struct drm_dp_mst_topology_mgr *mgr,
 
 	mst_edid = drm_dp_mst_get_edid(port->connector, mgr, port);
 	drm_edid_get_monitor_name(mst_edid, name, namelen);
+	kfree(mst_edid);
 }
 
 /**