drm/dp_mst: Destroy topology_mgr mutexes

Turns out we've been forgetting for a while now to actually destroy any
of the mutexes that we create in drm_dp_mst_topology_mgr. So, let's do
that.

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/20190903204645.25487-15-lyude@redhat.com

drivers/gpu/drm/drm_dp_mst_topology.c

@@ -4297,6 +4297,11 @@ void drm_dp_mst_topology_mgr_destroy(struct drm_dp_mst_topology_mgr *mgr)
 	mgr->aux = NULL;
 	drm_atomic_private_obj_fini(&mgr->base);
 	mgr->funcs = NULL;
+
+	mutex_destroy(&mgr->delayed_destroy_lock);
+	mutex_destroy(&mgr->payload_lock);
+	mutex_destroy(&mgr->qlock);
+	mutex_destroy(&mgr->lock);
 }
 EXPORT_SYMBOL(drm_dp_mst_topology_mgr_destroy);