drm/amdkfd: Set priv_queue to NULL after it is freed

This variable will be used to determine whether packet
manager is initialized or not, in a future patch.
Signed-off-by: NOak Zeng <Oak.Zeng@amd.com>
Acked-by: NChristian Konig <christian.koenig@amd.com>
Reviewed-by: NFelix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdkfd/kfd_packet_manager.c

@@ -278,6 +278,7 @@ void pm_uninit(struct packet_manager *pm, bool hanging)
 {
 	mutex_destroy(&pm->lock);
 	kernel_queue_uninit(pm->priv_queue, hanging);
+	pm->priv_queue = NULL;
 }
 
 int pm_send_set_resources(struct packet_manager *pm,